Ok, what I did now is the following: I have removed the .svg ressources and converted them to .png graphics. Now I don't do the loading via the program any more but now I do it only via the settings in the GUI editor. I don't think I have changed anything else of relevance, but now it works. So to me it looks it only has to do with the format, that svg wasn't working while png is. I thougth I had checked that already before, but I may have overseen something. So for now that's the solution, thanks for the reflection platform. ;-)
Stephan