Antenociti's has some nice variety. I need to get some more of their hex-bases for my JSA, just to get everyone onto the same base style. Before CB turned the Imperial Service into the Imperial SS, I'd been planning on using A-citi's tri-hex bases for them: The bases with curbs on them are very nice for removing smaller tactical rocks from your minis!
If you're not averse to some little extra work for some considerable savings, there's always the GreenStuffWorld rollers, there's some industrial and sci-fi ones, including the mandatory hexagons because TEH FUTURE!!!1
Why not transparent bases ? I picked some from customeeple for my OSS, the ones with 180° lof engraved.
If they're really thin, it works. The downside is that they can be easily scratched, which looks bad after a while. I'm using 3mm clear acrylic bases on my Zero-Gee Nomads, which gives a slight 'floating' look to the models.
I can't imagine a base without magnet myself that exclude transparent bases :p I like the micro art set : big enough to stuff all kind of magnets :p