In desktop icons are not alligned from sides evenlly. They are more to left size. It look like theres even enough space to move icon more to right but when i drag and drop it doesnt go there as if there wont be space. Also icons are more to top and at bottom is little more free space but not enoght to put icon bellow. Icons needs to be alligned to center and a little less padding from screen side is needed so i could use that extra line of space for icons. Also it will look more pretty if icons are alligned to center. Heres screenshot - left and top side icon to screen end padding looks the same but bottom side looks little more then top and right side looks like it has enough space to move icon there but i cant move it there.
This will be fixed in the 4.12 release of xfce and should also be fixed in xfdesktop 4.11/git if you want to test it there. Thanks for the bug report!