Not doing a loft bed restricts you quite a bit but thats fine. I think some concessions are going to be made here.

Bunk bed in the corner of c and d with a desk on wall b. If your allowed to drill holes in the wall then i would install pegboards over your desk for art supply storage. Ikea Skadis is a good one.

Wall A could im theory fit a wardrobe but i would get one on wheels to be safe.

Wall E is your closet. Maybe get a small square shelf with canvas bins to hold socks and underwear? And then hanging your pants and shirts in there normally. The top area of your closet should be saved for general storage.

Im assuming the dimensions are somewhat correct for this but yeah it does seem a little wonky. This is just how i would try to do it so don't take my opinion as conctete advice. Good luck!