Patterns! Ok personally I don't really like fancy patterns, unless there's really a nice one that appeal to me. I like to use polka dots, stripes, and checkered stuff, and they are really easy to do, you can draw them pixel by pixel.
I've got all these checkered stuff I did a while back, so I'm going to upload them for your use. :)

And if you want to create stripes it's easy too.
You can use any image program to do this, but I'm using Photoshop.
1. Create a new file, your width doesn't matter, but if you want broad stripes you choose a bigger value for height. For example I want a narrow stripe, so I use 10x30 (WxH).
2. I zoom in to 1000%.
3. Then I use the selection tool (M). Under the Style menu (refer to picture below) I pick fixed size and enter the values 10px and 15px respectively.

4. I click on the top part of the canvas.

5. Fill in selected area with desired colour, and repeat this for the lower part of the canvas and you've got your striped pattern!
6. To get it working, go to Edit>Define Pattern.
So making patterns are really easy, and if you have time you can draw stuff pixel by pixel and see what you get in the end!
I hope this helped you!