It's a problem that I've noticed for a while but haven't had the chance to look into it until now.
For the RadioFeeds plugin, I've noticed the icon doesn't show on the Android apps "Squeezer" and "Squeeze Controller".
However, it does show elsewhere like in LMS, Squeezebox Radio/Touch and Squeeze CTRL apps.

The image is 336x336 and in PNG format.
It also uses 24-bit color.

Where am I going wrong?

I've tried changing the image to different specs on the LMS machine (in Cache/InstalledPlugins folder") but have not seen any effect, even after a device reset, unless there's some kind of caching going on somewhere?