I will comment since you asked.
I have a few nitpicks, mostly to have to do with the faces. I really dislike the direction their eyes are pointing, it seems to almost give them a lifeless, vacant stare. Shepard's mouth bugs me too, it's nearly invisible. Overall, I can tell you were much more careful drawing Liara.
shapard was harder to draw, there is alot more detail in his line art then liara's,
but liara was painted better.
i might add to it one day,
there are a few small things i don't like about it either but it was taking too long to finish
its nice.
where is shep's mouth though?
also i like the way this looks, but they look like they are trying to balance on one leg or something.
mabye you could try this again, but add more time into both characters and backround. also mabye add fem shep?
long live fem shep/liara!