I love the colors you used in this dio man, really pops and keeps everything interesting.
When I use the corrugated cardboard in many of my customs, I do try to cover the edges with glue, then when i pain, I just paint over it and it disappears into the shadows.
I use cardboard OVER foam core to keep things light for shipping....and after all the glue and paint has dried, it makes for a pretty sturdy game or display piece.
Don't forget, your base has to be sturdy....weather it is the base of a terrain piece or the base part of a miniature.....i use many different styles of cardboards and heavy card stocks to achieve this...some corrugated and some heavily compressed.
Keep up the good work man,
Cheers,
Carl