My boyfriend needs a haircut and help?

So my boyfriend is getting is haircut. He asked me to help him. I know what looks good on me so I guess he umed I would know what would look good on him. Anyways I found a few cuts I like but I don't know if they would look good. Anyways it started when he pretty much shaved his head and he let it grow. So it grew into a shag but now its is so long in the back it is starting to look mullet-ish. He has a round face, thick, pretty straight, brown hair. What would look good on him? Pics would be great :]