I'll asume vignetting wasn't the only rejection reason? I see issues with softness, color, size, and centering as well. That having been said, it's not too bad for your first attempt, though I don't know if you will be able to edit it to standards for here. Assuming you can fix the issues I have just mentioned, the image will still be backlit, which in general, doesn't work too well for here. In any case, you can try giving this one a re-edit addressing the problems mentioned above, and we'll how that turns out.
If the original image is only 1023 pixels across, there is probably not much that you will be able to do. You should keep in mind that while very versatile cameras, super-zooms like your SX40 make great compromises in terms of quality to fit such a massive focal range into a single camera/lens combination. You shouldn't expect results to be too good in anything but the best light, and at relatively close range. Anything outside of those conditions, and you'll start to see quality issues, like with the image above.