(I am not a lawyer, but…)
If you are just planning to post this stuff on a website, I wouldn’t worry. I think you would be asked to remove the content long, long before anybody tried to sue you. In this case I think it’s unlikely that you would even be asked to remove the content.
However, if you’re planning to have this published by a publishing company or hosted in a high profile way by a high-traffic site, like for example the Blender foundation’s gallery or webpage, then it would probably be safest to avoid any potentially infringing things. There’s a lot of gray area on the web, (uh, YouTube, anyone?) but companies that have to actually take responsibility for their content first hand (YouTube has the plausible deniability that it allows people to upload stuff freely and responds to complaints, so it’s in a slightly different position) are going to be very careful.
A good example is something like this image by Zoltan Miklosi. It’s on his personal website and I think that there’s no problem with that at all. In this case, the Blender gallery might even be okay with it.
However, it was one of the submissions to the gallery for my own book, to be published by Sybex, and in the end Sybex decided it was better not to run it, just to avoid the slightest risk of any potential legal entanglements.
So, my short answer is, don’t worry about it unless you plan to A) make money from it or B) pursue any kind of mass-media exposure for it.