not to sure since i never been banned on imvu for this reason, im pretty sure imvu logs ips. for your offense u say (banned for Payment Fraud) don't know how imvu feels about that, either way u can try to create a dummy account if it that dummy acc gets banned then you know imvu is keeping track of your ip and does not want you to return to imvu period. << then i guess u can always use a vpn to get back on imvu.
on another note if that dummy account is not banned (give it couple days). if not banned/disabled then you should be free to start over on imvu with a new account but same IP. from my experience i was banned for trying to sell a account. basicly imvu told me i couldn't have the account back that i was trying to sell, but i was free to come back to imvu on a new account. not to sure if these rules apply to all offense against imvu.
also another option, you could always contact them and ask them if u able to start new on imvu.