Note: Most of this is talking about V1/V2 and how systems could be improved for v5.
Music/Ambiance: As far as I know, no RPGWO server has had music. I don't think the code would even support it. Maybe if you made a .wav and forced it to run as an ambient loop, but ... eh. Many people simply turn the music off, but for me at least, the silence is glaring. I think it should at least be considered for V5. If not music, then improved/extended ambiance. Birds, leaves rustling, frogs, and yes .. crickets. Maybe they could even be more dynamic so that you hear more bird sounds when there's lots of trees around. I think it would be a very creative way to add a lot to the environment.
Sounds: As it stands, sounds are fairly lacking. Many actions in V1/V2 don't even produce sound and the ones that do are usually kind of hard on the ears. I don't think too much needs to be done other than finding higher quality sounds and making sure more actions use them. Adding soft footsteps might be considered too, although it would be a bit more involved to ensure it's not annoying as hell.
I don't know anything about what you're using to code the game, but it might also be possible to make sound positional if it is being emitted from a source. The further away it is, the quieter it is (probably if it's 1 screen width's distance from the player, you can't hear it). Possibly tweaked to make it sound like it's coming from left/right/up/down of the player too. Just a thought.
Art: There's a lot to be said about the style of RPGWO. I feel the style should not be changed. However, some aspects could absolutely be improved upon. For as long as I can remember, the players.bmp has held the oddest assortment of characters spanning several different styles. Some actually look pretty good, others look like stuff someone jokingly made in mspaint. I think the general solution for this is to revamp the artwork, keeping the style but cleaning and improving. Easier said but ..
We can help! If you're dead set on producing the code yourself, we can at least help create the assets. I propose we have a subforum for these assets where we can upload art, sound, music, ambiance.. whatever. Maybe include polls so we can vote. The idea would be a collaborative effort to create assets that work together. Obviously you would need to approve of them. Anything uploaded in this way would have to be original work, and uploading it would relinquish any claim the uploader had to it.
I know so far you've seemed to generally oppose others helping in this way but .. hoping you'll at least consider it.