I have wanted this in the past but I can't remember what I needed/wanted this for.

I have an image that I would like to use as a display for the latest screenshot taken using placeholders and the /screenshots folder, but this is impossible without the System Interactions Addon (I dread using it in my modpack because it scares users away and users will disable it anyway).

No, please use the assets folder like everyone else. Having assets outside this folder makes things a lot more complicated for me and I don't want to deal with that anymore.