Although I did quite a few digital designs I wasn't really happy with many of them as nothing seemed to repeat properly without just mirroring everything (which is generally frowned upon as it's a very basic way of doing things and doesn't always create the best results, although personally I think it works really well sometimes). With this in mind I went back to a couple of my original drawings and traced them off so I could adjust them to repeat properly.
This is basically done by cutting the image into squares, moving those around according to the repeat you want to create and filling in any gaps or joins that you don't want. If you want a detailed explanation that actually makes sense try googling the magic square method. Anyway, I used those to create a half drop and a brick repeat which I think work pretty well.