Board Game Grid

Hi and thanks in advance for any help. I want to create the board for a board game that consists of a grid. I have the board of the game in a texture, although it isn't a power of 2. What is the best method to create tiles for my texture? The concept is a 2d game similar to tic tac toe and it can be played in different boards. One would be a 6x5 another would 10x5 for example.

Currently my thought is to use box colliders, or invinsible quads for each tile and add the behavior to them. One of my problems for this is that the quad isn't aligning exactly 1 to 1 to my texture and i will have to either a)add all tiles manualy by duplicationg or b)add the tiles by multiplying i think the x position by 2. Both solutions won't work if i am given later a different texture for the board.

The second problem is that if i want for example to highlight the tile i have selected or mouse overed, the color would cover the art of the original tile that the board has. Anyone has any ideas of how i should proceed with these problems, especially the first?