Is the wall where the water pipes come up an outside wall, or an interior one? If interior, I'd consider moving them to inside that wall, assuming that's where you want the shower valve. As to moving the drain, you essentially have two choices on a shower: a linear drain near one wall (most common situation), or a traditional drain preferably centered in the shower. If your drain is centered, it makes it neater since you can have similar slopes all around to the walls. WRT the drain, you may also want to move the vent into that wall. The joist at the bottom of that wall makes it a bit harder (you'd need access from the room on the other side, or from below), but probably the best way to do it. Hard to tell unless you're there. Some people like to have the shower valve close to the entrance, so you can turn it on and adjust the temp prior to getting in there - it doesn't have to be close to the showerhead - you can put it nearly anywhere you want.