One issue that I always have trouble with is stuff that stores sell that is obviously very close to pre-exsisting copyright material.

Technically we are allowed to use what we purchase in commercial endeavors, but there are a few items that are way to close for comfort.  Daz Troll is a classic example (ie: Lord of the Rings Cave Troll).  There was a forum discussion way back about a vehicle in one of the stores that closely resembled something for one of the Alien movies.

Since I do sometimes use what I buy for commercial work, and I have published a web comic in the past and I do intend on doing more complex commercial work in the future, I try dilligently to avoid these "inspired by" items.  Unfortunately it is a "buyer beware" issue.  i have purchased a few items form these categories that I later learnt were very close to other intellectual properties.

I'm not saying things like this should be pulled out of the stores, as there is a market in fan pics and such, but I really would like these things to be earmarked in some way.  But alas, I digress.