If the decals don't work, here are the reasons why and how to fix them. Please post any other questions or concerns here. If you have a feature request, make a discussion and I'll reply when I have a chance.

1. You likely have an addon with conflicting decal replacement files. This can be anything from another decal replacement, or even a map that has it's own replacements. 'GM_Gleb' is one of those maps. Unsubscribe from the addon and enter "menu_cleanupgmas" into the Console from the Main Menu. If that doesn't work, check your 'garrysmod/garrysmod/addons' folder and remove any old addons.

2. You may have decal replacement files hardcopied in your garrysmod/garrysmod/materials/decals folder. Simply delete them.

3. You may have to restart Steam. This is the most common issue with decal addons, they often require a Steam restart. That's all!

Please post any other issues below. Cheers!