My Bird Collage...A Finch I think..

When my Thursday painting group meets I usually work on a collage. This is the first time I have tried do almost the entire collage with paper. The only part painted is the flower centers. All the paper I collage with come from magazines or newspapers. I glue the papers down with acrylic gloss medium and use a brayer to make sure the papers are adhered really well. When the piece is done I brush on a final coat to varnish the work. It always seems that I get some papers that lift and ripple ....not sure why. The hardest part of doing this collage was trying to establish some value differences. I would love some comments; do you feel I need more some value differences?