What's a cheap going rate for Website Graphics Design?

Hi guys,
My friends have started up a web design company and have told me that they’ll pitch some of my website designs to their clients and I’ll get payed if they chose my templates for the website. They do want to know how much I would charge them for a design. I don’t know how much I should charge?

I need to specify that I am required to do ZERO codding of the sites and it’s just making the graphics required for the site for example: a front page, text page and images page.

If you guys know of any sites I could check out please let me know!
Your advice is appreciated!
Thanks guys.

I like this vein diagram. Are you making wordpress themes and modding them/ populating them?