I love fun projects like this! It seems like you're restricted to 5mb (Imgur's limit), perhaps there is a way to chain multiple images together? I wrote another project in the same scope [1] where it uses Discord files and compiles everything to a massive blob then splits it up into many smaller chunks, giving an (in theory) infinite upload cross domain. Seems to be still going strong.

[1] https://github.com/5ut/DiskCord