Partly right! The only mistake is the verb. The correct sentence is this:
"We ARE proud that you are our users".
1: using "have proud" is not common
It isn't common because it's wrong! "Proud" is an adjective, so you can't say "We have proud" - this is grammatically impossible.
2: using plural with singular you is wrong
It is fine to say 'you are our users' . The 'you' here is plural. I don't see why you think it is singular.