I can't enlarge it for some reason to see the fine details, but for a possible tattoo sketch these are fairly good, depending on how large of a tattoo your friend wants. The smaller a tat is, the less detail you can put into it without the lines all blurring together after the years. For sketches, yes, I think these are good. :) Don't worry about getting "THE" style for body art, as all body art has different styles. Find YOUR style and run with it.
The only tips I could offer would be that if your friend wants these LARGE, then you have a loooooot of detail/shading work to do (the male angel's robe looks kind of shiny?). If your friend wants them about 4-5 inches tall, from top to bottom, then I would actually suggest removing a little detail from the flowers. For the female angel, I love the way you did the feathers as a stylized little line all the way down. It's awesome. And it would look great on skin. With a bit of pale blue shading and some white over tones when inked, it'd look badass. :o Keep those wings, man.
Klimatic: Dude, if you want angels in bikinis with a huge rack, that's cool. But there's nothing wrong with his "female anatomy." Just looking at the halo and the robe she's wearing, and you can kinda tell it's done in a classic angelic style, like in paintings centuries ago.
Anywho. I do wish I could get the click-to-zoom thing to work. Either way, you're off to a good start. Keep tweaking em, but the idea is solid. :D