Uses a single avatar URL, allows to override gravatar with a custom URL for avatars in interface_config.js.

interface_config.js

     /**
      * Whether to only show the filmstrip (and hide the toolbar).
      */
-    filmStripOnly: false
+    filmStripOnly: false,
+    RANDOM_AVATAR_URL_PREFIX: false,
+    RANDOM_AVATAR_URL_SUFFIX: false
 };

modules/UI/UI.js

     }
 };
 
-UI.userAvatarChanged = function (resourceJid, thumbUrl, contactListUrl) {
-    VideoLayout.userAvatarChanged(resourceJid, thumbUrl);
-    ContactList.userAvatarChanged(resourceJid, contactListUrl);
+UI.userAvatarChanged = function (resourceJid, avatarUrl) {
+    VideoLayout.userAvatarChanged(resourceJid, avatarUrl);
+    ContactList.userAvatarChanged(resourceJid, avatarUrl);
     if(resourceJid === APP.xmpp.myResource())
-        SettingsMenu.changeAvatar(thumbUrl);
+        SettingsMenu.changeAvatar(avatarUrl);
 };
 
 UI.setVideoMute = setVideoMute;

modules/UI/avatar/Avatar.js

-/* global Strophe, APP, MD5, config */
+/* global Strophe, APP, MD5, config, interfaceConfig */
 var Settings = require("../../settings/Settings");
 
 var users = {};
             }
             users[jid] = id;
         }
-        var thumbUrl = this.getThumbUrl(jid);
-        var contactListUrl = this.getContactListUrl(jid);
+        var avatarUrl = this.getAvatarUrl(jid);
         var resourceJid = Strophe.getResourceFromJid(jid);
 
-        APP.UI.userAvatarChanged(resourceJid, thumbUrl, contactListUrl);
+        APP.UI.userAvatarChanged(resourceJid, avatarUrl);
     },
     /**
-     * Returns image URL for the avatar to be displayed on large video area
-     * where current active speaker is presented.
+     * Returns the URL of the image for the avatar of a particular user,
+     * identified by its jid
+     * @param jid
      * @param jid full MUC jid of the user for whom we want to obtain avatar URL
      */
-    getActiveSpeakerUrl: function (jid) {
-        return this.getGravatarUrl(jid, 100);
-    },
-    /**
-     * Returns image URL for the avatar to be displayed on small video thumbnail
-     * @param jid full MUC jid of the user for whom we want to obtain avatar URL
-     */
-    getThumbUrl: function (jid) {
-        return this.getGravatarUrl(jid, 100);
-    },
-    /**
-     * Returns the URL for the avatar to be displayed as contactlist item
-     * @param jid full MUC jid of the user for whom we want to obtain avatar URL
-     */
-    getContactListUrl: function (jid) {
-        return this.getGravatarUrl(jid, 30);
-    },
-    getGravatarUrl: function (jid, size) {
-        if (!jid) {
-            console.error("Get gravatar - jid is undefined");
-            return null;
-        }
-        var id = users[jid];
-        if (!id) {
-            console.warn(
-                "No avatar stored yet for " + jid + " - using JID as ID");
-            id = jid;
-        }
-        if (!config.disableThirdPartyRequests) {
-            return 'https://www.gravatar.com/avatar/' +
-                MD5.hexdigest(id.trim().toLowerCase()) +
-                "?d=wavatar&size=" + (size || "30");
-        } else {
+    getAvatarUrl: function (jid) {
+        if (config.disableThirdPartyRequests) {
             return 'images/avatar2.png';
+        } else {
+            if (!jid) {
+                console.error("Get avatar - jid is undefined");
+                return null;
+            }
+            var id = users[jid];
+
+            // If the ID looks like an email, we'll use gravatar.
+            // Otherwise, it's a random avatar, and we'll use the configured
+            // URL.
+            var random = !id || id.indexOf('@') < 0;
+
+            if (!id) {
+                console.warn(
+                    "No avatar stored yet for " + jid + " - using JID as ID");
+                id = jid;
+            }
+            id = MD5.hexdigest(id.trim().toLowerCase());
+
+            // Default to using gravatar.
+            var urlPref = 'https://www.gravatar.com/avatar/';
+            var urlSuf = "?d=wavatar&size=100";
+
+            if (random && interfaceConfig.RANDOM_AVATAR_URL_PREFIX) {
+                urlPref = interfaceConfig.RANDOM_AVATAR_URL_PREFIX;
+                urlSuf = interfaceConfig.RANDOM_AVATAR_URL_SUFFIX;
+            }
+
+            return urlPref + id + urlSuf;
         }
     }
-
 };
 
-
 module.exports = Avatar;

modules/UI/side_pannels/contactlist/ContactList.js

 function createAvatar(jid) {
     var avatar = document.createElement('img');
     avatar.className = "icon-avatar avatar";
-    avatar.src = Avatar.getContactListUrl(jid);
+    avatar.src = Avatar.getAvatarUrl(jid);
 
     return avatar;
 }
             contactName.html(displayName);
     },
 
-    userAvatarChanged: function (resourceJid, contactListUrl) {
+    userAvatarChanged: function (resourceJid, avatarUrl) {
         // set the avatar in the contact list
         var contact = $('#' + resourceJid + '>img');
         if (contact && contact.length > 0) {
-            contact.get(0).src = contactListUrl;
+            contact.get(0).src = avatarUrl;
         }
 
     }

modules/UI/videolayout/LargeVideo.js

 function updateActiveSpeakerAvatarSrc() {
     var avatar = $("#activeSpeakerAvatar")[0];
     var jid = currentSmallVideo.peerJid;
-    var url = Avatar.getActiveSpeakerUrl(jid);
+    var url = Avatar.getAvatarUrl(jid);
     if (avatar.src === url)
         return;
     if (jid) {

modules/UI/videolayout/SmallVideo.js

     if (!this.hasAvatar) {
         if (this.peerJid) {
             // Init avatar
-            this.avatarChanged(Avatar.getThumbUrl(this.peerJid));
+            this.avatarChanged(Avatar.getAvatarUrl(this.peerJid));
         } else {
             console.error("Unable to init avatar - no peerjid", this);
             return;

modules/UI/videolayout/VideoLayout.js

         }
     };
 
-    my.userAvatarChanged = function(resourceJid, thumbUrl) {
+    my.userAvatarChanged = function(resourceJid, avatarUrl) {
         var smallVideo = VideoLayout.getSmallVideo(resourceJid);
         if(smallVideo)
-            smallVideo.avatarChanged(thumbUrl);
+            smallVideo.avatarChanged(avatarUrl);
         else
             console.warn(
                 "Missed avatar update - no small video yet for " + resourceJid);
-        LargeVideo.updateAvatar(resourceJid, thumbUrl);
+        LargeVideo.updateAvatar(resourceJid, avatarUrl);
     };
 
     my.createEtherpadIframe = function(src, onloadHandler)