Might be an idea to escrow a certain amount of bitcoins by someone that is trusted within this forum to improve your reputation just a little bit.
IIRC, there was a mixing service that used a trusted forum member to escrow a certain amount of coins, all to ensure that in case the service doesn't pay out, the escrow funds would cover that amount. So yeah, this is basically the only way to prove that you're here to conduct fair business as mixing service.
min 0.003 BTC, max 112.52129268 BTC
Too bad that there's no way to verify you actually have 112
BTC 
Considering the fact that no one will ever entrust over 100BTC to a freshly started service, why not have a chunk of these funds be held by an escrow? It would definitely give future users of your service a peace of mind.
And they exit scammed at the end LOL. If someone is going to use an escrow to gain trust, they NEED to let everybody know that they will remove the escrow several days before they do it. Otherwise, they can wait until they get a good amount of coins, get the escrowed coins back and run.