This may have been suggested before, but could we have some kind of rating for the shops?

There is a huge range of quality between items, and also a large difference in prices.

Perhaps the shops could be rated by a mod (or special 'rater' person) or maybe just have a free system. So you can get gold/silver/bronze etc medals depending on the quality of your stuff (like the custom Psypoke ribbons)

Because there are a lot of shops (not naming anyone) that should really be posted in the fan-art section, as the work is of a lot lower quality than can be made. The fan-art section is there so that these sorts of people can improve their work, and I have no problem with them not being amazing there - as nobody can be immediately... and they should get some feed-back.

Oh well... that probably sounded a bit, harsh/elitist/pretentious... but you can just tell me how stupid I sound

No. Slateport is the place for all shops; it was split from the Fan Art forum specifically and intentionally.
Other than that, I don't really have an opinion on your suggestion. It sounds like it may be difficult to implement, but it could be a valuable improvement.