Our crafty artist Anton Bauer created a little tool with which to fix your GUI-Textures for Icons. Simply 'Drag&Drop' your mod’s corrupted Icon / UI - Textures on the supplied batch file and it will compile, overwrite and save your files. All you have left to do after that is re-upload your mod. You can find the script in the SpaceEngineersModSDK
I didn't find the right solution from the Internet.