Art trades, Requests, and Surprises are images that one artist will make for another artist, usually featuring individual and original characters as opposed to canon ones. These pictures, once uploaded, can be sent to the artist whom it was created for, when the original artist selects the Art Trades/Requests button for the picture while in the Edit Pictures section on the artist's user page.
Art trades are simply a trade of art between two artists. The participants will either request a certain character situation and other specifics or will ask to be suprised. Both artists will then create and upload their 'half' of the trade, Artist A drawing what Artist B asked for and vice-versa. art trades are formalized by any form of communication - e-mail, comments, Lilymud, private messages, whatever suits both parties the best.
Requests are similar to art trades with the exception that only one artist is drawing. An artist or user would request the other artist draw them a certain thing and expect to do nothing in return. This form of inter-community art is not as popular as Art Trades because only one party is working and expecting nothing in return. Sometimes people commission an artist; this is similar to a request, with the exception that the requester pays that artist for their services.
Surprises, also called gift art, are the final type of inter-community art that one artist can create for another. A surprise is when one artist draws a picture for another without any prompting. Surprises can be summarized as similar to Requests, as one party is drawing for the other and expecting nothing in return; however Suprises are usually acts of kidness as opposed to being expected or asked of from the reciever.