With pink being a more feminine color, I would paint the upper half a blue or green. I'm not sure what shade of pink the tiles are, but I feel that the blue or green could offer more of a masculine effect if there are men using the bathroom. Even if there are only females in the house, I think it would still balance out the colors well. Even a kelly green (still a little feminine) would probably tone down the pink.

If you want to have the room look light and open, you will probably want to go with a light shade of green or gray. Black or dark gray or even dark shades of blue also go well with pink but they may make the room seem smaller. The colors to use also depend on the shade of pink in your bathroom, such as dark, medium or light. Grab paint chips from your local paint or hardware store or mass merchandiser and hold them up to the pink tiles to see how well they go together. That should give you a better idea of which color to use.