For your first tileset, this is quite an impressive piece of work, despite the simplicity of the ground tiles. As others have stated, the flora are very well-done and are quite in line with the conventional Knytt theme.
I made a sample screen with it and I must say that it's
very versatile with backgrounds. I've scrolled through the backgrounds and found a lot of compatibility:
There are, however, a few issues. There are several tiles that "overlap", so to speak, and that's why you do not see all of the tileset in the sample screen. Furthermore, the way you've organized your tileset allows you to maximize number of tiles, but may inconvenience many designers. I've highlighted overlapping tiles in red, and have reorganized the tiles in a more comfortable manner:
As you can see, you lose eight tiles from this. The Juni lying face-flat on the ground is a great idea, but I think it might be better suited as a custom object? As for the other floating blocks - those are actually a strong element of this tileset, because they match the colour of the grass. Also notice that on one of the purple blocks, there is a single white pixel. Just a little thing to tidy up.
My advice would be to use 2-3 colours of a specific hue range. I find that the cyan range seems to work best, but I guess others could find a way to use the other colours. Anyways, this would allow you to free up 24-48 tiles, which would not only allow you to put in the grey blocks but would open up other possibilities.
Finally, the little tileset bar at the bottom is
brilliant, with the palette and all. Can I steal that idea for my own tilesets?
You also forgot to finish the 'M', so it says Tileset Experinent.
I hope this advice/criticism is useful, but I see lots of potential in you, sir.