「色紙」 tag?

I don't think we currently have a tag for those drawings that artists do and give away at conventions and such. They are recognizable by the characteristic squarish size of the paper used, and are generally photos of traditional_media. Examples include:

• pool #1135
• omchicken /trad; futami_yayoi /trad
• post #372495, post #376699, post #299575

The pixiv tag for these is 「色紙」, shikishi, which more accurately refers to the paper itself. pool #1135 translates it as autographed sketch. What tag would be preferred? Perhaps an alias?

It's pretty specific (too specific for just autographed_sketch) but seems tag-worthy to me, so I'd favor the japanese term, shikishi.

As I go about implementing this tag, I've found that some artists (e.g. ayuayu, mizame) work on shikishi paper/dimensions as a matter of routine rather than just for giving away at conventions.

The fact that a given post was drawn on shikishi paper seems a taggable concept as well, which leaves me torn between my original intent (limit to convention giveaways) and the strict dictionary definition (anything on that specific paper format), or perhaps separate tags to distinguish between the two.

They do look visually alike, but there are a few things that could help set them apart:

• shikishi handed out at conventions are often, though not always, autographed, dated and/or inscribed with the name of the convention (and artist's booth number).
• they tend to be much less complex and look less "finished" since they are often quickly drawn on the spot.
• artists that routinely use shikishi paper are obvious upon inspection of several of their works.
• pixiv title/commentary/tags can provide more information.

For the time being I'm going to lump it all together; can be sifted apart later if enough people care about the difference.

lumping sounds fine.