Hi!
The experience bar is all in your head . One of the main points of teeworlds is that it is pure player skill that counts - for motivation that should be enough, too. Although some might miss the artificial "simulated skills" that enhance motivation in games like WoW and most others by making you feel like you would get better by just pressing a button repeatedly: you can get used to relying on your own learning for motivation after a time as you - not just your avatar - get stronger (if you don't quit).
If it's some sort of visual social status / reward you're looking for: On thing to do is simply just always playing with the same name. Players will learn to remember it faster than you think (in open / ad-hoc games with only a few "Pro Players" in between, especially the good ones have to to play effectively) and even remember details about how you play + whether it's a good idea to attack you. P.E.: Look closely at how many "cannon fodder noobs" the enemy flag carriers "throw at you" before they try to finish you and stuff like that!
Also maybe start helping / pushing the "we-need-accounts"-people, whatever they are doing at the moment. Don't really know if they're really planning to implement some statistical / archievment-based or whatever public profiles, but I'd guess there should at least be some in between with that in mind...?