Add some nice watercolour textures to one of the corners to create a bit of interest (we'll do a bit more of this later). The texture I used is one I created myself and you can find a selection of them here. Use the Hue/Saturation panel to tailor the colours to your taste, and use the Eraser Tool on a low opacity to blend the edges into your background.

Use the free downloadable filter Mac's Remove White to remove the white background.


You can merge all the layers to help keep the document size down.