Hi and welcome to SB.com! I have done some similar projects for my home and liked the Mod Podge too for finishing the sealing layer. But I used plain old Elmers white glue, thinned with a little water to adhere the paper/cardstock to the painted wood. Be sure to let this first application dry well first. I also did some with nice wood grain designs showing thru for the people who like the natural look. I used my big red sizzix machine for cutting my shapes, but there are also many punch out designs available now for minimal cost.
Now there are also some spray adhesives out that work great but for me they were not cost effective( I got one at a local hardware store). Have patience I am sure there will be more responses as there are so many members here with all kinds of cool ideas Also whichever route you decide to go watch for sales like Michaels or Joannes coupons and mark down bins (Sorry I am on a low budget and try to do that with groceries too) I figure the more reasonable priced a craft is the more we can afford to do it at the right price! plus for you increase your profit!
Best of Luck and Have Fun!