You can still use fabric with a smaller repeat. Using fabric with a smaller repeat means that you will get less variation in the blocks you produce, but it can still be quite pretty. And you can increase your variety by how you orient you squares before you sew them into blocks - suppose you get two squares that both have mainly color/shape A in one corner and color/shape B in the opposite corner. In one block, you can have the color/shape A near the center, and in the other block, you can have color/shape B near the center, and you will end up with two very different looking blocks, even when starting with very similar squares to build the block.
For seeing how fabrics will look in a one-block-wonder (which is made of triangles, not squares), this
design tool is a great way to see how fabrics look. I suggest playing around with an image of your fabric with the tool and see what you think. (Triangles will be different than squares, but it will still give you a sense of how much variety your fabric will give you, and you can see how changing the orientation can give more variety.)