Some of the chapter websites have pictures of their houses. I know Flordia State University and LSU, and Oklahoma Univ. do. Besides that you kinda have to search around. Once I saw a postcard on ebay with a picture of the Alabama University house. So far from what I've seen all of the houses are stunning. The LSU website even has pictures of inside the house! I've never been in sorority house (they are outlawed in my area) but from what I've heard they are usually very well kept.
Here are some links
Flordia State:
http://www.fsuphimu.com/
LSU:
http://www.phimulsu.com/index.asp
Univ. of Nebraska-Lincoln
http://www.unl.edu/phimu/
Oklahoma Univ. :
http://www.ou.edu/student/greek/oupan/00pm.html
Also on a side note, here is a pic of the quatefoil fountian at Ole Miss that was donated by Phi Mu.
http://www.olemiss.edu/orgs/phimu/fountain.htm
LIOB!