I meant another type of blur, that will hide the poor cropping.

Basically:

Duplicate layer.

Set top to Overlay, and opacity to about 60.

Use Gaussian Blur on the bottom, and opacity 100.

top one can be Lighten too.

It'll make it so the jagged lines dissappear.

Also, if you're not going to remove it, at least move it down a bit. So you don't have it cut off immediately. Though from what I see, it's a wallpaper made for 2-tiled taskbar. Since if you drag the taskbar up (so it's 2 times what it was), it ends perfectly on the bottom-right picture's line.