[Tutorial] How to make a custom decal!

[Dobbydoo]

I can see my decal in the editor, but it won't show up ingame. I've tried to remove the cache files, but it still won't show up. Does anyone have a solution to the problem?
Also, if I place it in the editor, save, quit and enter it again it won't show up in the editor either, but I can click the place where I placed it and delete it. If I go try to select a new decal, the editor will crash, and to solve that I have to delete the new decals I've used permamently.