Need help with home studio in very odd-shaped living space

Hello everyone! I am new to recording and also to the forums here. I am just getting started out with my Pro Tools/DigiRack system and I have just about all of the equipment I need to being recording. I am a fairly experienced drummer and I also play guitar and bass a little. I live in a detached 2-car concrete block garage that was converted into a guest house for me to live in while I go to college. My father is also in the process of adding a small room to the back of the garage for my use. Anyway, changing the construction of the walls is pretty much out of the question because space is at a premium. However, I am open to any suggestions that may improve the sound quality of the space. As of right now, there is no acoustic treatment whatsoever. I (and occasionally my band) use it as a practice space and the sound is very harsh. The kitchen in the upper right corner has a concrete floor, the bedroom in the upper left corner and the main room in the middle are carpeted, and the new room at the bottom will have laminated hardwood flooring. The entire space is drywalled and I want to try to leave it open (except for the bedroom and bathroom) so I can take advantage of the extra space. I've also considered making the bedroom my control room. The bedroom and kitchen have ceiling heights of 6'6" and the main room and bottom room have irregular-shaped ceilings as described in my crude drawing below (sorry, guys -- didn't have time to figure out SketchUp well enough to do 3-D). I am just looking for any input about how I could go about treating this space. I apologize if I haven't been specific enough about something -- if so, please let me know and I will get the information posted ASAP. Like I said, I can't do a whole lot of construction, but I am open to anything (including new walls perhaps) and possibly ripping up the carpet and going with the laminate. Thank you for your time and I hope to hear back soon. -Robert

how is the sloped ceiling on the bottom room oriented? based on the space, you might just get away with some corner absorbers all around and/or some slat resonators in the bottom room.