It would be nice to have a "graphic" object tileset, but that's still made of symbols, only more varied than the current letter selection. A good example would be the Abigaba/Chozo tileset for Nethack:
http://www.multifoliate.com/nh/ (Edit: embedded a modified version of it below).
I like having letters or symbols instead of little pictures, because I find the former easier and less eye-straining to identify than the latter, given how small the tiles are. There's also an aesthetic and cleanliness that I like about abstract graphics. However, I get annoyed at how several creatures share the same letter: for instance, given the frequent goblin ambushes, I find it disquieting to see 'g's approaching my woodcutter, until I realise that they are really groundhogs and not crossbow goblins. This would be much alleviated if the 'g's for the goblins and groundhogs were of a different font style, and maybe with some subtle decorations, (see the Abigaba tileset).
This could also be a solution to prolong the usability of the current graphics style. Toady was mentioning in the last interview (on gamasutra) that the letter E is kind of over-used; I think different object tiles with the same letter in different font styles would go a long way to alleviate that.
So, unless #1 himself picks up the idea, who's up for making this new tileset
?