After experimenting with the effects on Photoshop and Photoshop Elements, I wasn't satisfied. I've decided to make my own backgrounds, scan them in and use them in my design. I bought some watercolour paper because it's thick and it's easier to create different shades and effects on it. I used a transparent, brown ink and scanned the papers. Here is a slide show of the scans(four scans of seven pieces of paper including blank papers to manipulate on Photoshop):
