Cut Paper Light-boxing
This technique involves layering cut paper to create the illusion of depth with filtering light. With a light source placed behind the layered paper, you can capture the detail of each layer while combining all of the layers to create the desired effect.
Personally, I am intrigued by the abstract nature of many works of cut paper lightboxes, but am still looking to define a theme that will carry throughout a few pieces.
I have been experimenting a little bit so far, mostly using an iPad to imitate the effect of physical paper layers.

When translated into paper, these coloring would be inverted based on the placement of the light source (as with the image below).

Artist Question:
I am looking into creating a work or series of pieces that follow a theme. I am not exactly sure what type of theme I am looking for, which is where the question comes in. What do you think I should base my theme off of? I am open to nearly anything, I just want to make my project cohesive and interesting!
Your preliminary drawings remind me of the water/ocean waves so maybe doing a simple underwater scene would be cool! Or maybe an above water scene with dolphins (sorry I grew up near the beach!) Another idea could be a night sky and you could maybe make the light dynamic and do a shooting star!
I think it would be cool if you did a theme of the four seasons of the year, and had each piece be lighted with four different colors that represent each season.
I think your original idea that you suggested in class of making the theme based off of Avatar was great as it not only provides a clear 4 elements to base a series of four pieces off of, its also a topic you seemed passionate about and I personally find myself more invested in creating artwork the more connection I have with it.
I agree with what a lot of other people are saying. I think it would be a good idea to choose something that has a clear and defined set of things that fit into the theme, whether it be the seasons or the avatar elements. But having the set number of things in the theme I think will make it a lot easier for you to make your art.
I think having a theme that you really enjoy would make the project fun and personal. From your introduction posts and artworks it looks like you like nature so a floral series or a forest series would be interesting! I definitely think the four elements from Avatar would make for a nice cohesive piece.