Here are some general ideas:

Anything old can be made new with fresh paint.

Wall Art – Anything goes here. You can buy cheap canvases and paint anything on them (if your lean toward modern a simple geometric patter would look great.) Just try to use, for paint, the colors that are already in the room

A memo/bulletin board – Buy a cheap (from Walmart) cork board and cover it in fabric (you can use a spare sheet, a curtain panel, or anything that is currently in the room.)
Staple (from the back) coordinating ribbon in a criss cross fashion and use it to hold photos, messages, whatever.)

Make your own lamp – Buy a cheap lamp kit and you can convert just about anything you like into a lamp but don’t forget to customize the lamp shade. You can paint it, hot glue trim, etlc.

Pillows – Add pillows to your bed that compliment your bedcover and other colors in the room

Curtain Tie Backs – Get really creative here. You can tie silk flowers around the curtains or bend an old fork to use as a tie back – you are only limited by your imagination.

Best of Luck