What should I decorate my room like?

Can I add rhinestones to my walls?

It sounds like you want a pretty room, and you can definitely put rhinestones on the walls. I've done it myself.  Here is what I did to add rhinestones.

Get a stencil that you like.  In a room like yours, you can add a stencil that represents something you like about gypsy/renaissance.  Big flowers, leaves, etc are all great for a theme like that. I did large leaves in the room I stenciled, and started them down by the floor and took them halfway up the wall. When I was done, it looked like large plants growing from the floor.  Take the rhinestones and a hot glue gun (get your mom to help if need be). Glue them in strategic places within your stencil. I did a trail around and through certain leaves.  It looks really pretty.

If you have really big rhinestones (mine were small), you could put fake frames around them and glue them to your wall.  Add a small water fountain in one corner. It is soothing and would work in your theme.

For curtains, use long, colorful scarves. Clip them to the rod with curtain clips, and alternate colors.

On your floor, try a pretty area rug that will tie your colors together. Something like this Multi color area rug would be perfect in a room with orange and green.

Have fun! Sounds like a very pretty room.