for the rollerblading ones, try to make it so that the picture is interesting without the person in it. it should be able to be a photo (although, without a person it may be a little bland) without the guy in it. when you put the person in the frame, it will be that much more interesting.
i like the first one of the second set you posted, as well as the third because you can see the silhouette of the house in the third.
"When people say you have a one track mind, tell them they're only half right. Skiing leaves 2 tracks!" - Seth Morrison