The shape is also a little different sometimes. Bigger tits, smaller tits, extra-skimpy are the variants I see.
But, well... I checked up to slightly before 1.0 and never noticed anything else but the standard X-Com one-piece. You sure you're not confusing this with Piratez?
Edit: Also, male agents don't really have much variety, either. Two guy variants with thongs vs one chick, and some rare embellishments on the trunks. No idea how you're seeing these as all that different from the gals.
Out of curiosity, went back to 0.7.2, which is the closest I have to when swimwear was introduced. The nearest to 'different swimsuit' I got was this.