You:

I think this wallpaper looks good, simple is simple, and simple is beautiful in this way. But for my opinion, I think the sky and grass don't handle well, I think you can bright them a little, especially for the sky, because I think the wallpaper's mood is "happy", but the sky color still looks a little "sad". Grass color looks nice, but a little more green make it more "love", don't you think?

You:

For the vector, if it's your first vector, I think it works well. Didn't you use the vector method like that: You don't draw the line first, but draw a big shape with line color, then draw other shapes for the color. For that method, it works well for dynamic lines, but I think you can edit the color paths to make it a little more regular because you used stroke line for the sky. ^_^ Flowers are lovely.