If #23 is the snowflake at breakfast, and you're using the Mod, then it isn't working in the modded game for some reason. As noted, you can get it in the unmodded, but there's some kind of disconnect in the coding when the mod is installed. The same problem occurred with image #21 in 0.5, but it worked fine in 0.6. They will likely resolve the problem for 0.7, but, if history holds, one of those items will be a problem in that release.
I also think #24 was the same kind of thing (something like a sex toy in the restroom - can't really remember the object, just the place). Same story as #23. Unmodded seems to work fine; modded does not, at present. Why they could get some, but not all, of the hidden images to work with the mod/patch in I can't say, but it does seem to be a recurring issue the last two releases.