check out the thread by golden tooth on his new tank.
he has a pic of his sump there...u might wanna have a look at his sump design.
other than that, doing a search on the interenet for "DIY sump" or "sump design" will yield you some webbys where u can see some designs too.
most importantly, the sump has to have sufficient space for you to put in ur skimmer and the return pump.