Add an /avatars/#UserId route which redirects to the user's current avatar every time, so you don't need to update remote references to it

config/routes

@@ -7,6 +7,7 @@
 /sitemap.xml SitemapR GET
 
 / HomeR GET
+/avatars/#UserId AvatarR GET
 /feed FeedR GET
 !/#EntryKind/feed FeedKindR GET
 

src/Application.hs

@@ -48,6 +48,7 @@ import System.Log.FastLogger                (defaultBufSize, newStdoutLoggerSet,
 
 -- Import all relevant handler modules here.
 -- Don't forget to add new modules to your cabal file!
+import Handler.Avatars
 import Handler.Common
 import Handler.Entries
 import Handler.Feed

src/Handler/Avatars.hs

@@ -0,0 +1,12 @@
+{-# LANGUAGE NoImplicitPrelude #-}
+{-# LANGUAGE OverloadedStrings #-}
+module Handler.Avatars where
+
+import Import
+
+import Model.Cache ( getCached )
+import Settings.StaticR ( staticR ) 
+
+getAvatarR :: UserId -> Handler ()
+getAvatarR = redirect <=< fmap (avatarR . entityVal) . getCached
+    where avatarR user = staticR ["img", userAvatar user]

templates/mf2/h-card.hamlet

@@ -2,7 +2,7 @@
   $maybe route <- mcurrentRoute
     <a .u-uid.u-url href=@{route} hidden>
 
-  <img .card-img-top.u-photo src=@{staticR ["img", userAvatar user]} alt="Avatar for #{userFullName user}">
+  <img .card-img-top.u-photo src=@{AvatarR userId} alt="Avatar for #{userFullName user}">
 
   <div .card-body>
     <h4 .card-title.p-name>#{userFullName user}