For me not using the first pic wasn't about being conservative (Some beauty campaigns cut it closer - see prev thread on the Sienna "make it moist" ad)
Part of it is because it's you in the pic and it's your services you are offering.
Perhaps if it the pic was actually of the nails in focus and there wasn't part of the nip showing - it may work with correct wording - 17-25 appeal...
But... I find most of my repeat clients are 26-55 - you may alienate these.
I'm 27 - not prudish, not shocked, but the picture wouldn't make me call and book if i saw it - just because i wouldn't immediatley start thinking "beatiful nails, i want them done". (which an advert is supposed to do).
The second & third pics are like hentai pictures (japanese cartoon porn) Which again do not scream nails.
Make it an eye catching, simple picture which, when you look at it you think "lovely nails" not "cracking juggs".
Kudos on the modelling though. Takes some bottle! xxx