So...I've decided to update my desktop today and first things first: the wallpaper. Basically, I had a plan but got seriously confused by the grid on the desktop. (Oh and to make this clear, I'm laying out my desktop via the wallpaper, so I need to figure out the grid in order to make my sections the right size).

I went into personalisation, set the Horizontal grid spacing and vertical both to 60 (I'm presuming that's pixles).
In photoshop I made a 60x60 doc, stroked the edges with 1px width. Set that as a pattern, filled over my desktop (on a new layer of course) with the pattern to get the grid. Set everything out in proportion to the grid, but then when I set it as my desktop background the sections I had made didn't fit with the icons...

Can anyone help me figure out how to tackle this?

My resolution is 1920x1080. https://dl.dropbox.com/u/57101485/Example.jpg is the 60x60 grid that I made.

EDIT: (Oh and don't mind the mess, I've been moving stuff and checking sizes...it's not normally like that - I swear!)

The icon size is the size of the icon graphic (the setting is called 'Icon'). Two other settings, Icon Spacing (Horizontal) and (Vertical), add to it. There may also be additional space by default as a buffer around the icon graphic, so adjust accordingly. Play around with numbers until you find a combination that fits and looks good.

Was hoping to avoid the good old trial and error technique Looks like it might have to be that way regardless.