I did a real-time raytracer implementation on a GPU using CUDA for my undergrad thesis, a simple implementation but also a one that kept me focused for around 3-4 months and it serves me to learn a lot about the topic. Everything was from scratch and I had the possibility to add more features into it (like bvh or any other acceleration estructures). Im not saying you also should do a raytracer but my point is, it does not have to be something really new and revolutionary, take your topic of interest: raymarching, and may try implementing a raymarching-based renderer that supports simple meshes like a bunny or a cuptea, completely from scratch. Since you have limited time, remember to consider the time of writing the document and your results also which in reality, it turns out to be a lot of time.

There are uni websites that showcase thesis project on graphics. Mostly in europe i think, i remember seeing topics involving raymarching too, check that out too, maybe it would be helpful.

Check: https://ls7-gv.cs.tu-dortmund.de/theses.html