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;材質的部分似乎是受限的，不過模型部分好像比較沒問題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裡面也有提到：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.也就是說，不修改，不獨立使用的話，把它包含在你的作品拿來當作商業用途都沒問題。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.這邊也提到，不把下載下來的作品獨立使用，僅包含在自己創作的一部分的話，自己的創作拿來賣也可以。當然，實際上來說，你都要改成漫畫了。模型被你改成2D，然後顏色光影什麼的可能都變成你自己弄，別人要認出來，除非是很特別的模型，不然也不容易吧。不過，轉貼了這麼多法條，我想說的是...如果希望畫技進步，還是練習靠自己畫背景吧因為以人腦畫出立體背景，不使用照片或3D描繪，完全是可以靠練習，訓練自己辦到的事。