Very good initiative @steempress & https://steempress.io/
Referral program is always a good tool to help growing user but please make sure that a referral program is designed well so that only real and active user signup. We had a website where initially introduced referral program and website was flooded with users but the sad side was that out of these user only 1-2% were actually using the website and rest never came back.

So my suggestion will be to introduce effective referral program to help grow both the part(Referrer and the service provider, in this case steempress.io )

Best wishes from my side & do let me know if I can contribute by any means :)