To be honest I almost consider it a must have, because I love how human fantasy\imagination works in contrast of having a picture forcibly showed to you, but Idk if a funcional way to implement this actually exists, so here's my suggestion. Implement a way to hide pictures (ok maybe not the cover) inside threads as default, with a one click "show it" (for the single image) for those who actually want to "spoil themselves" Idk if this can also have (positive) implications on the load of chyoa or the linked services (aka imgur). PS: the idea also came because of a story I'm following where the author decided (after feedback) to clone the story itself between a "pictures path" and a "no pictures path"
Similar to SFW Mode. As a workaround, you could resize images with CSS to a width and height of 0px. (It might be possible to only affect images in chapters but not the cover image.) If it is a Game Mode story, they could also use a variable to show/hide images.