1. More attachment areas
I already made a post about this, so I'll just summarize. In addition to the current areas, I'd like to see right, left, lower, AND upper arms and legs, and multiple attachments for some areas, such as the head and the torso areas.
2. Attaching from Inventory
I'd like to be able to right click on an object in my inventory and select which area to attach to, and have it automatically rez and attach itself. Conversely, I'd like to be able to "Take" things while still wearing them.
3. Making your own Gesture Animations
I'd also like to be able to make my own animations for my av. Kerstin also mentioned this, I believe. Even better, if you could make certain gestures interact with one another, such as shaking hands or hugging. Preferably, the method to making an animation would use a visual-type interface like building an object, and not scripting, if possible. We could even sell gesture animations to other people!
4. "Poses" for avs
Going along with the "Making your own gestures" suggestion, we should be able to "pose" our avs. Currently, we can make pose-like gestures, such as the "cross arms" gesture, but it quickly goes away, leaving the av in its normal standing pose. Perhaps a button could be added to the gestures window to make it so your av stays in a certain pose until you move. Also, one might want to pose and still talk, so you could make it so that after the "typing" animation, the av returns to its previous pose.
5. Making your av lay down
Sometimes I just get really tired.
6. Adding a llteleportav command.
I am most definitely NOT a scripter, but adding a command that teleports an av to another area, another sim, or another object in-world would make for some interesting travelling. Orrey's already got a Stargate set up. It's just DYING for a teleport script. It told me so.

7. Support for other sound formats
MP3, MIDI, even OGG. They're all either compressed or very small, so they wouldn't eat up bandwidth. Actually, you'd be able to get more sound quality and a longer sound with MP3 and OGG than with WAV. MIDI is also very good because of the small file size. Which brings me to...
8. Longer sounds
Longer sounds would be nice. Perhaps we can upload whole songs and place them in an object that looks like a stereo? Of course, longer sounds like whole songs would be limited to objects only, as putting whole songs on gestures would be going a bit too far, I think... Every time you smile or frown a whole song'd play, heh. Would get anoying fast.
9. Maneuvering while sitting (and laying down)
When I sit on an object, I always sit on the side that's currently facing me. A lot of the time, this is the wrong side. I'd like to be able to simply use my arrow buttons or something similar, to move around on an object, instead of having to get up and walk around to the appropriate place.
Well, I guess that's it for now. I can always edit my post later if I come up with any more. Happy new year!