https://3dwarehouse.sketchup.com/tos.html10. 3D Warehouse Materials; Use RestrictionsB. Use RestrictionsYou may not:Modify 3D Warehouse Materials (other than your UserCommunications or Models or content you posted) oruse them for any public display, performance, sale,rental or for any commercial purpose except asexpressly authorized in these Terms of Use or theGeneral Model License;材质的部分似乎是受限的，不过模型部分好像比较没问题1. License GrantB. Authorized UsesThe license to the Models granted above is limited toCreating derivative works of Models (“Creations”),including by substantially modifying geometry, color,or other attributes of the Models, provided that ifyou upload any Creation to the 3D Warehouse, you...Distributing Models, Creations, and Combined Works tothird parties for your business purposes (includingfor commercial purposes);
http://help.sketchup.com/en/article/3000049在FAQ里面也有提到：4. I am a reseller of household appliances. I want touse models of manufacturers' appliances from 3DWarehouse in my marketing materials. Is thatpermitted?Answer: Yes, so long as they are not transferred asstand-alone items and trademarks and logos aremaintained and are not removed or altered.也就是说，不修改，不独立使用的话，把它包含在你的作品拿来当作商业用途都没问题。3. I'm an architect. Can I sell my designs whichinclude models from 3D Warehouse?Answer: Yes, so long as the models you downloadedfrom 3D Warehouse are not transferred or sold asstand-alone items.这边也提到，不把下载下来的作品独立使用，仅包含在自己创作的一部分的话，自己的创作拿来卖也可以。当然，实际上来说，你都要改成漫画了。模型被你改成2D，然后颜色光影什么的可能都变成你自己弄，别人要认出来，除非是很特别的模型，不然也不容易吧。不过，转贴了这么多法条，我想说的是...如果希望画技进步，还是练习靠自己画背景吧因为以人脑画出立体背景，不使用照片或3D描绘，完全是可以靠练习，训练自己办到的事。