You could be more careful with the foreground & background selection.This is a cross bike(minature)...So this should be placed on dirt to be more realistic.Now...for the sunset you would use the same poster you used in this photo with the difference that you would place it far from the bike(it would be blured in the background & i would look like real).I don't know what are you shooting with but don't place your object THAT close to your camera lens because some spot's (of the bike) are out of focus(OOF).Try to find your camera's focus range.

The hyperfocal distance is the closest distance at which a lens can be focused while keeping objects at infinity acceptably sharp; that is, the focus distance with the maximum depth of field.You can do this on a table.Take some paper & put some dirt(from your garden)on it.Then place your bike on the dirt & your poster in the background.Then see from your camera how does it looks (the whole set up) & make the corections that you like.At least thats how i would shoot this photo!This is only my opinion author & i hope i helped.I wish you good luck!!!

Great attempt

agree about the dof