This is a journal page I did today and the background is done using them. You put Gesso on the pages first and the Gelatos blend very easily. I also added some stamps and stencilling in the background for texture, applied some rub on text and a couple butterflies with rhinestones. Lots of fun! :-)
The only thing I will do a bit differently next time is when applying the Gesso, I may try using a spatula. When I used a brush, it left so many lines, that it looks like scratches in the Gelatos background. I'm sure that might be ok if you want the texture but I think I might like it smooth, with some raised areas. I suppose it would depend on what you're wanting to end up with.
If you want to give it a try, I highly recommend it. Check out YouTube for a bunch of tutorials, too. :-)