Upload & Sell: On
Linking is a good thing for this forum, IF the link has something to offer the reader, or has a set of images that should not be posted here (for size reasons, or for copyright reasons).
Links that are solely for the purpose of self promotion are generally a bad thing IMO. IT will open floodgates and become a link farm. Useful discussion will diminish and useless links take their place.
If you know its a useful, non self promoting link, I would say great. If you know its just to gain some love for yourself (ultimately), I think it should be avoided.