For the v4.0 beta releases I've just been listing a generalized listing of whats changed.
The detailed changelog can be found in the forum
https://oss.azurewebsites.net/forum/showthread.php?t=14315
It takes a very talented person to make 16x16 icons, and even more so its extremely difficult to make a one for FlashFXP due to the shape and characteristics of the logo.
I've attached the icons we use in FlashFXP, if you think you can improve on them I'd be grateful. The tray uses 16x16 XP for newer versions of windows and 256 colors for older versions or low color depth.