1: This does not appear to be pixel art. It looks like these were done using a variety of tools in PhotoShop or a similar software package. Also, you only have 2 examples of your work. The rules state that you need 4 examples of smaller work like that in order to open a showcase.
2: It looks okay. It has some nice texture, and looks like it will fit in nicely with some of the default tiles of RPG Maker VX. The only problem I can see is the grass does not blend very well when mapping with a bunch of tiles at once. There is a nice line that forms, which is not really so nice. Try editing it a bit until there is a seamless transition in between tiles.