I'm not sure about this so don't quote me.
I think that signatures would be fine because they are for the ECC forums. However, I don't think a paper model would be allowed bc they would be mailing a physical item to you in exchange for EcoDollars.

 

an image, once uploaded never disappears off the internet, it can be downloaded, and reuploaded, etc. So I would say that once you receive the item, you'll have it forever, and there would be no risk of lost money. (It's a given that it has to be ECC related, of course)
A physical item can break, get lost, it may not even be sent, etc. It's outside of our control, and therefore something we don't allow.
A signature, custom graphic, avatar, etc, has to be ECC specific of course.

 

Although there is some clarification already posted, I'd still like to post. xP

From my time on many forums and games with rules like this one, generally anything that is directly related to the forum / community / game and is digital/virtual, it is allowed to be bought/sold by/for the virtual currency. Signatures, YouTube videos, animations, art (once uploaded, and not physically mailed), music, et cetera is allowed - they are not "in real life," hold-able, tangible, or physical. However, if they are turned into something like that (a print of the art, a CD of music or video, etc), it is not allowed.

If you can touch it in real life or use it in the physical world, then it would be against the rule(s). If it is strictly digital/virtual - and of course ECC-related - it should be allowed.