In J!1.5 in administrator go to components, contacts, contacts, and either edit or create new contact. The last item on the left side of form is to add a contact image from your images folder. Choose one from the drop down menu. It will need to have been pre-sized.
I posted a similar question and was trying to get a graphic next to the contact form like I did on an old DotNetNuke install...never got it looking right:
Whoa now, I've seen you round these parts, and there is no way I'm talented enough to give you advice. I've seen some nice contact pages around here, you need to go ask those folks. I'm a waaaay novice, just giving back the tiny little bit that I can. But design advice, I'm way out of my league.
A pretty contact page is down in the bottom third of my need to do list. When I get there, maybe we could learn together.