craftgrrl | First attempt at decoupage

I have painted and decoupaged an ikea mini chest (small wood chest) with pictures that I printed out and found in magazines. I have used mod podge to glue down all the pieces of my project but now I need to finalize/protect it either with a spray lacquer (specifically for decoupage) or layers of mod podge/decoupage finish. I really like how it has turned out so far but I am concerned that spreading layers of mod podge on top of my project will cause bubbles or the edges of the image to curl that I can't smooth out like I did when initially glued the images down. My concern with the spray lacquer is that I don't have warm temps and/or well ventilated area to spray in.

Does anyone have experience with adding protective coats to paper crafts either with a spray lacquer or mod podge and what would you recommend? Should I still be concerned about bubbles being created or is that not an issue now that the initial gluing has been completed? Thanks for your help.

The picture below is just one of my experiments with laying out images onto the wood box which is why some of the pictures looked crooked. Not the end product.