I would start with an aqua blue on the walls -- very versatile if you decide to change your theme later on. I have SW Open Air in my laundry room (I actually had a semi-beach theme in the space up until recently). You could paint the cabinets a bright citrine like Funky Yellow or perhaps more chartreuse/lime. If you want to keep them white, you could add some removable wallpaper to the door panels to create an inset cabinet look. Of course, you need to hang a surfboard on the long wall! Orange would be another great accent color. If there's space, I would turn the bed to be parallel with the window, with space to walk around the sides. A vintage trunk or stack of suitcases could work with this vibe, serving as a side table with lots of great storage. Keep the bedding a simple solid, maybe white, but add a fun pillow. And add a colorful rug if possible. Here's what I came up with: retro beach.

I am assuming that are not going to replace the tile floor because that would be expensive. A great desgin to work with your floor would be a hawian inspired surfer desgin. your existing yellow wall color would work but I would paint the walls a light cream. Stain the closet doors and windows a dark cherry. Here is an image of the furniture I would do. Keep it simple with a bed and two storage night stands since its such a small room