It is totally okay to post non-Mario art here! Said the guy who has, in the last month, has posted three Mario-related drawings out of about seven. But hey, I think the forum title should just be "Creations" or something like that.
Yes, you're onto something in terms of art style with those first two. The second is actually... hypnotic. If you want my advice, work on perspective for realistic-ish things like the last one, while the distortion into the distance of "The Annual Heart Parade" adds to its charm. It looks pretty good otherwise. For instance, I like the scratches of orange in the sun.