Well...
Should I continue with FD?
There's more than one version of a single sprite, so I don't see why you should discontinue your version.
Definitely. I am really liking the island stage.
Try some dithering in the backgrounds and maybe increase the contrast a little for the backgrounds.
If you want to learn a little more about these concepts, have a look at this.
http://www.vg-resource.com/thread-25474.html