The NYT has a slideshow of sheets and stuff for cribs that are "not boring." That'd be fine if boring were the problem. More often, the problem is sickening cuteness or schlock.
I point to them here only for use in an extreme emergency; if you or your partner is adamant about buying some insanely bad baby bedding, just consider these options first.
On second thought, skip all these flowery sheets and just get some BbBasics Jersey Sheets in solid colors from Buy Buy Baby.