i have no idea about en vogue shapes. my right hand nails are kept rounded and short, and my left hand basically has claws. (for some strange reason, nail polish lasts forever on my nails. after a hot bath, i noticed one tiny piece chip off a nail desiogn i wore for a week straight. all girls i know envy me for that and thin kit a waste to let a guy have nails like that)
color-wise, i have seen quite some dark colors lately. chanel even made black and glittery charcoal shades for their current ensemble and in "germanys next top model", heidi klum wore dark polish on her hands all the time. (but i found her nails a tad too short for that, but thats probably just my preference - as extremely dark shades really exaggerate the shape of the nail against the brighter hand, i think dark nails need to be reasonably long, otherwise, it looks like chewed-off stumps. yuck)
id look more for colors that fit your style and clothes than what is thought to be fashionable right now. if you like to have attention on your toe nails, i could imagine some fun with iridescent polish. (recently saw a shimmery peacock blueish green O_O)
placing objects like rhinestones on the nail sounds like a fun idea, too... i need to keep that in mind.
a friend of mine has some gothic lolita magazines, and the nail stuff they got in there is incredible. long (!) artificial nails, hand-painted in the most fun ways (symbols, bats, basically all you can imagine), and sometimes even with small holes punched in to have a little chain from pinky to ring finger nail. thats just sooooo cool. (omg, im such a styling whore)