Wait what??!
1) How does Sketchup know you used their program to outline your background?
I mean I use Sketchup for academic purposes and for designing my own projects, and if I need to - I trace it and render it manually in PS.
Unless you were talking about taking screenshots and using it in as a comic background, which obviously would make sense to be banned.
2) If it's your own model, don't you have a right to do whatever you want with it?
I really need an answer please
Also as an alternative you can use Rhino - it has a complicated learning curve since it's professional-oriented, but you can do anything with it once you learn using it. Much easier than Blender