Yep, my bad. Must have gotten then mixed up when pasting them down. Had them correct in my notes. Good catch!
To be honest, I don't think there is a part after the gif page. If there is, the answer seems to be beyond esoteric. I have tried every combo with the image names and they have all come up empty, yes even doubling them and such to a reasonable extent, so either there is none or you need to brute force it due to some arbitrary filter.
Also the line: (IDK if this counts as a spoiler or not)
The end result must be the number. Maybe it will lead to something in the future but all there seems to be now is a dead end. Unless a dev pops in here with a hint or someone brute forces it and finds the next, I will be bowing out. I have spent far too much time on this as is.