Cool!

And btw - you're on - As soon as work calms down (I'm tired of 12 hour days now) I'll put a lot of effort into my RTS again

I have done the diamond shape isometric maps before and cannot find a reason to do them in preference to a tilebased isometric approach which is in the long term a lot easier to code, understand and to do pathfinding for. Think carefully about your reasons for doing it in diamond shape.

For sprites use Reiners sprites until you have your own. They work nicely and have enough animations to look good. He doesn't have any Robots though. - for my RTS I have someone doing sprites for Robots and the rest of the units will be Reiners tile sets. (He does have zombies)