Personally, I think it's funny. As an ex-stand-up comic I look for humor. As an artist I'm also looking for anything that's aesthetically appealing. Avatars satisfy that urge, sometimes.
But as a poker-player I also think it's a small window into the player, themselves. I think I/you can tell a little about a player from their avatar selection. If it's a photo of them or a loved one (child/sig-other/pet) they usually play predictably. If it's art or from the counterculture, I see a bunch of over-bets and all-ins. If there's no avatar, then I'm left guessing without any assumptions, just their name.
Now, this is just an observation after 14 years of playing online. As a live player I feel I'm just conditioned to observe and take stock in players appearance at the table. To me there's no difference online.