Nice looking suburban...LOVE IT!
The wheels you appear to be running are what look like factory spare rims with beauty rims added. You should be able to pick up some factory 15X8.5 rims fairly cheap...search e-bay like Dave mentioned (use "rallye", "ralley", or "rally" in your search...you will find lots!). The hardest thing will be finding "nice" centers and rings to go with them...and don't skimp, get nice ones to match the rest of the nice work!
BTW - is that a late model roof rack?...looks cool!
On a side note, my truck was the exact same color as your from the factory, only mine had white in the center.
-Jeff
**EDIT**
stay away from newer rally wheels such as these, IMO they look to "plain".
http://cgi.ebay.com/ebaymotors/ws/eB...&category=6782
Here are some 6-lug rally wheels I found on e-bay in case you were interested...
http://cgi.ebay.com/ebaymotors/ws/eB...&category=6782
here are some alum ones...
http://cgi.ebay.com/ebaymotors/ws/eB...category=33748