Here is my 2 cents.
1: Your default language for your webmaster program is CZ.
That scares the shit out of 90% of all US webmasters, They got no clue what it is and think it is a "new russian scam"
Change that to default English, might be a good idea to completely remove it, or have CZ on one site and EN on another. Anything that a webmaster can't understand scares him.
2: Your membership cost €30 per month, I saw no USD pricing, most people form USA want pricing listed in USD since they dont know how much 1 euro is.
If you need to have pricing in Euro, show the aproximately cost for USD.
3: You pay only ~30% to webmasters, €10.50 from a €30 membership is not going to cut it. You are compeeting with programs that pay 50% -75% recurring. No matter how much more the webmaster will earn from using your program, they see it as low income, because other people pay higher % so they will make more.
4: You have some promotion videos, why not make some galleries that webmasters can link to directly with their ref code. The more work the webmasters need to do themself, the less webmasters will signup.
5: A webmaster referral program is ALWAYS good, if you wish to grow fast, you need sigwhores on the big boards, might not bring in instant webmasters but it is good branding for you name.
6: Are you from Prague?? Partying in Pragua is fucking amazing, throw some parties with your models and webmasters
