Heh, I wanted to practice what you guys told me last time a wee bit, but my internet went out before I could grab a stock. So, I took some of my own. Photos Spoiler
My photo instructor said you should only rarely use flash.. because the flash is very distracting and it makes the image look unnatural. Also, it's best not to shoot in the sun unless you want a silhouette (which is an overdone concept, which is why it's not favored by most photographers. That and it eliminates a lot of detail.) And the composition is very strange in this. Try to focus on a subject, it's too random as is. The second is too blurry. Try to steady your hand when you shoot. Also, you should focus in on a specific subject matter, like just the bike and the shadow, not a bike, grass, a shadow, a fence, and a strange distracting shiny thing in the background because it looks cluttered and unappealing. Nice idea though for the second, just need better execution. BTW I've taken three photo classes and have a Nikon D5000 (which is an amateur SLR camera). I'm not an expert but I think these things I mentioned could help. Edit: I realize these are for stock purposes. I'm wondering what you were going for when you took these?
Basically what Erico said, and to elaborate slightly on the flash thing, try not to use it unless extremely necessary, especially in stock photos. Having a flash shadow can ruin something that would have potential, but becomes unusable because of some random shadow across a usable piece of material. That, and, if you are going to pursue photography, having flash shadow is very distracting. If you need a flash though, use a soft flash if your camera is capable. If not, just try to overexpose your camera (most cameras have a half-click-to-focus function now days) to a nearby lightsource like the sun, and it should dull the light around what you're trying to take a picture of when you go back down. If it's not out of focus. I've done this a few times with my old camera which was a little hand-held beast about the size of a pack of cigarettes, and it seems to do the trick half the time. I'm by no means a professional photographer, and have only recently bought a very decent DSLR camera (which I have yet to take any good pics with yet), but several people have told me I should take up photography because I "have a knack for it" or some ****. I just try to take interesting pictures, and people seem to like them, so it's win-win, I guess.