I'm new to monoprinting, but the technique is so fun, esp. for background prints for other projects. I used some things around the house to make texture plates:

I used the large Gelli plate using Golden and Studio paints brands. I like to use one color in 2-3 different shades. But you can see that I strayed from that fairly quickly when I started building layers - threw some gold in there too for shimmer.

I'll use these to cover books or make ornaments (the holidays are just around the corner!)

Check these sites out for more ideas for textures and results:

May your bobbin always be full

Blue Twig Studio

Printmaking without a Press - Linda Germain doesn't use Gelli plates, but uses sheets of gelatin, old-school style - WOW!