Yes, I think this is a different situation. The typical process for prints of paintings is for an artist to go to a printer to have giclee prints made. I think large flatbeds are used. I don't see anything like typical inket prints of paintings being sold at art exhibits, art shows, or in artists co-ops, etc.
Until it was brought it up I hadn't thought about copyright of the artwork as well as the photographer's copyright of their photos; I don't know how that's handled. Try photographers organizations like
American Society of Media Photographers - Homepage or PPA.
If an artist wants photos of the artwork to market or display online, then the photographer could provide digital images. When I've done juried exhibits I submit a digital copy, and if it's a lumen print, cyanotype, Polaroid, etc. I scan those (hi-res). I found scanning 2 D work produces much better results than photographing them.
For whatever will be provided, FIRST do a contract specifying usage (for how long, where and how the images will be used, etc.). THEN set up a shoot and take the photos. If additional usage is requested later, then a contract would need to be done to cover that additional usage.
What's done for cosplayers is similar in sports to photos used at autograph signings. Typically those are provided by the team and would have been part of work contracted by a team photographer with the team (or might have been part of a work for hire situation although more is done freelance these days). This doesn't seem to be that type of situation, except maybe an artist would want a print of one or more of your photos to put up in an art center or something? Can't say I've ever seen that done; a photo of someone's artwork might be in a brochure or pamphlet or on a poster for an upcoming show or exhibit.