I like pine and gray together with the white.. I love white sheets, but perhaps you might consider gray and white pattern. Urban Outfitters always has great items that you can mix and match to create your own style Don't forget some art for the walls to provide some interest.

You could do blue.

The lighter Seagrass or even new blush color sheets would like nice. you have a neutral palette so you can change your sheets have new looks at will.

Some inspiration from IKEA