did you keep some of the game pieces? try using them on the flaps. Not hugely bulky pieces, but gaming cards and bits of board can be blended in quite well.
So again tear out some strips of patterned paper, as you did for the covers. these are the pieces i used for one of my pieces.
MOST IMPORTANT tip, remember that 2 flaps will point up and 2 will point down, decorate them accordingly, you don't want your images on upside down.
Play with the torn strips and magazine images to find a placement you like.
try out your words too, altho you wont add the till last it is still a good idea to work out where they are going to go in relation to everything else.
Begin by colouring around the images and paper with watercolour crayons or water soluble wax crayons, then go over this while still wet, with acrylic paint. blend it all in well. the edges will not disappear totally, but they will merge with the background.
Keep layering colours and acrylics, till you have a pleasing effect. Don't forget to keep the tiny black border clean.
Glue on your words, and colour them and outline them. Add some stamped images. In this one i added some dragonflies. you only need 3 or 5 stamped images, more than that will be too much. always use an odd number.
Add some darker colours under the images for shadow, and outline the words in white, using the edge of a credit card.
Here are all four flaps finished. See the rounded corners all facing into the middle, and the folded parts on the outsides. remember 2 flaps face upwards and 2 hang down.
Here are some close ups.
You can really see all the layers of colour and paint.