I've noticed this past week that in my games, the image preview is often delayed several seconds, but they do appear eventually. I've also noticed that when dragging tokens to the map from either a character sheet in the journal or from the compendium, it can take several seconds for the token image to appear - I see a blank, white square on the map the same size as the defined token before the correct image finally appears. Macros are also slow to operate: I have macros that use TokenMod to toggle light sources on and off, and TokenNameNumber to number multiple instances of NPCs, and the effects of these macros and scripts often take a long time to appear, sometimes causing me to check if the sandbox has crashed.