CS5 Extended has multi-layer fill. If you create a texture with your tile (probably want to run a 50% offset filter, too) you should be good to go. I don't know if you are running this revision, but it might help. If you're running an older version, I believe gIMP also has multi-layer fill for textures, you should be able to perform this step in gIMP and then pop it back into PS without any deprecation.

You can do this all using Javascript. Here's a quick little script I've written, it will copy your image into 100 layers, each 10px by 10px:

/*
--------Photoshop Script - Grid to Layers------------
Author: Oisin Conolly
        www.DigitalBiscuits.co.uk

This basic script will create new layers from your active layer, each equal in size according to the grid dimensions specified.
*/


//this is the size of our squares in pixels
var squareSize = 10;



var docRef = app.activeDocument;

//set the ruler type
if (app.preferences.rulerUnits != Units.PIXELS)
{
    app.preferences.rulerUnits = Units.PIXELS;
}

var layerRef = docRef.activeLayer;

for (y = 0; y<docRef.height; y+=squareSize)
{
    for (x = 0; x<docRef.width; x+=squareSize)
    {
        //activate the original layer
        docRef.activeLayer = layerRef;
        //make the selection
        docRef.selection.select(Array (Array(x, y), Array(x, y+squareSize), Array(x+squareSize,y+squareSize), Array(x+squareSize,y)), SelectionType.REPLACE, 0, false);
    
        //copy the selection
        docRef.selection.copy();
        //create and paste new layer
        docRef.artLayers.add();
        docRef.paste();
    }
}

To use it, save that file and load it up with Photoshop by going to

File > Scripts > Browse

Make sure the filetype is set to *.JS

If you want to change the size of your squares just open the JavaSCript file in Notepad, change the value for squareSize and save and run it.

* EDIT *

If you want to do more advanced things with this script, you can download a Photoshop Scripting reference guide which lists all the classes, functions and variables you can work with. (For example how to rotate a layer).

The above script uses JavaScript syntax, however you can also use AppleScript, and VBScript to work with Photoshop.