Oh and I never mentioned them to be Sith. Dark Jedi and Sith Lords do not make one. Sith Lords are Dark Jedi, but Dark Jedi are not nessecarily Sith Lords.

Either way, if I point you guys to the way the DB is set up, we have three orders to choose from :

Sith, Obelisk and Krath.

The Sith are the politians/warlords type

The Obelisk are the true warrior

The Krath are the scholars and sorcerers

That is how they are defined without the Dark Brotherhood of the Jedi, though of course, they are not fully true to the Star Wars EU. (On the other hand, in a sense it could be, as the storyline of the Dark brotherhood is set 10-15 years after Palpatine's death (which marked the end of the last true Sith.)

In that picture, the man, Ferran, is an Obelisk, while the female (which I'm currently reworking from the tips I've had on this forum) is a Krath.

Speaking from my completely useless art background-

Most of what I would mention (technical stuff) has already been brought up, so let's talk about composition. The flow of the first image is quite nice- Apart from the sword and the flowing cape, all things draw the eye back to the center of the image. But that's a small issue, as the comosition is good overall. The second image is pretty straightforward. However, I can't give any sort of concrete opinion until I've seen the images shaded. (If that is indeed what you plan to do.) A bit of high-contrast shading could certainly enhance the mood you're trying to create.

As for the nit-picky stuff, I'm afraid the nipple thing gets to me too. It's not like I look at it and say "oh god, that's inappropriate", becauase it's not. It's just that all this business with the buxom and scantily clad women of fantasy artwork seems so... well, cliche. But I absolutely detest following the crowd, so take it whatever way you like. The other little thing that got to me for some odd reason was that the first image kept conjuring images of Final Fantasy and osther such Japanese material. I don't know, maybe it's just the sword and the armour. No such issues with the Naga Sadow image, though.

All in all, good work. Keep it up.