My first idea was to create a 2d array for my columns and rows, but it seems like there should be a better, or possibly cleaner, way to achieve this. Each square on the grid is going to have a background image, probably a .png although I might just draw the images with a draw method. Basically, I want to be able to drag and drop images onto the individual grid squares. I've been searching for a solution and the closest thing I can find is the tiled map solution. That just seems like a little overkill for what I'm trying to accomplish. Also, I don't know if this helps but i need my grid to be 12 by 12 and take up the entire width of the iphone screen.
Use tiled map editor compatible with cocos2d.
A tutorial on this subject: http://www.raywenderlich.com/1163/how-to-make-a-tile-based-game-with-cocos2d