Redecorating..need an older room ASAP [10 pts!?]?

i have light blue walls with seashells around the tops of my wall in my room...well i was 12 when i did this, its been a couple years now and i NEED change..i cant re-paint it for a while..im hoping i could maybe see if the left over paint outside is still good and cover the fish and stuff? i cant use wall paper..i was thinking of getting the huge rolls of paper..drawing on them and putting that up..but see sadly my grandfather is really strict so i gotta be careful what i do, like no taking the paint off or anything, other than that it should be fine, idk how hed react to the paper though...any ideas...oh and the furniture too ive had it since i was reallllly little and its just too big and in the way..my bed has a foot-board and headboard..and it really is just too big and takes up most of my room, i would put the mattresses on the floor, like a normal person [well all my friends] but my mom complains about dust and if bugs get on it so what can i do?..and my bed and dresser and everything is kinda ugly..i need a more grown up room..and im into all the gothic/emo/scene stuff..and whenever my friends come over they always question my room why its for a 12 yr old..so yeah i need ideas FAST!..WITHOUT buying anything cause my mom wont let me go out and buy anything cause she doesn't have the money..well shes saving to get me my new computer since mine broke..so i need help asap :) Thanks in advance!!