I like the tree/branch thingy. there's some really neat pencil marks in it. the house looks sort of rushed or something, though. you did call them practice sketches though, so whatever get you drawing is good!
Yea, I'm not a building drawer. I'd like to try the same thing, but in pen. I feel like it would come out a lot less... crappy. I'm so frivolous with the pencil, I can't get straight lines. At least I'm trying! (And it definitely was rushed because I didn't want to draw it really, I just had nowhere else to sit and that was the most interesting thing there... haha)