I think the 3 images you used for the frontpage are too small, which causes them to not fill up the entire block. Can you try and use bigger ones? The images should be at least 268px wide.
Regarding the slider, I think I mentioned this in another topic as well, but the misalignment of the slider is caused by your own modifications. I can’t give you support on that. Best would be to copy the slider part from the css in the package you downloaded from themeforest, and use that to undo the modifications.