You can request just about any scriptable feature on your avatar, and I'll tell you how viable it is.
Here's a few examples of common features I add to my avatars:
Emotes are a fun way to express yourself around other players!
Works really well with animated eyes. Also can be mixed with animations (see below).
I use Blockbench to create custom animations for your avatar. I charge based on the complexity of the animation, to me.
Some minor scripting elements can be added, ie. texture changes like winking, particles like hearts or bubbles, or activating the animation via a trigger or button press.
I can optionally provide armor support - that is, custom modeled armor that fits to your avatar's body.
I use my script to add as much compatibility as possible with mods, however not all modded armor will be compatible. There's nothing I can do about this.
Feel free to request something not listed above! If I think I can implement it, I'll give you a quote for how much I'd charge for the feature.
See the Price sheet for some examples.