This pretty idea is something I made for my DDs several months ago - framed monogrammes for their bedroom doors.
They look good, don't they?
All you need is a frame (mine were 2 for $5.00 from Big W); paint; and assorted papers.
The frames I got were already white, but because they were only cheapies I gave them a cupla coats of white paint to cover any marks/ scrapes on the wood (happy to do that - after all, they were only $2.50 each!).
You may prefer to use a colour to match the room instead.
You will find the painting easier if you remove the back of the frame as well as the glass.
You won't need the glass if you are planning on attaching dimensional embellishments.
Set aside to dry thoroughly.
While the paint is drying (or in my case 3 weeks later...well, life's busy!) cut your background paper to size and adhere it to the backing of the frame.
I printed the monogrammes on the computer and used them as a template to trace onto the paper I had chosen for the letters. If you're really clever you can draw them freehand.
Adhere letter to background paper, add desired fancies and...voila!
This would suit a boy's room too, using robots or space creatures or monsters, grrr!