Just for shits and giggles, I tried the following individually: (v0.4)

1. post #1049426 - 0 results. No surprise here.
2. post #1005112 - 0 results. Kinda surprised. I figured it would find at least 1 other chair image.
3. post #974624 - 0 results. I think zero_pictured images stops it from working...
4. post #521328 - 0 results. Has a copyright this time (Star Fox) but still found nothing.
5. post #1144516 - 0 results. animate_inanimate this time, no species or characters.
6. post #1157879 - 0 results. Character and copyright tags present but no species tags (or many other tags for that matter).
7. post #1157971 - 3 results. Character and copyright tags present but no species tags. Lots of general tags. Finally found something but what exactly did it look for?
8. post #1159014 - 0 results. Species tagged, others not. I'm guessing character, species and copyright tags don't make a difference. Looks like solo was ignored as well.
9. post #286706 - 0 results. big_breasts tag present, but not much else. Low tag count seem to kill it.
10. post #315433 - 0 results. Zero pictured, ~40 general tags.
11. post #765898 - 6 results. Some basic gen tags present. All results had the same character, maybe character tags aren't ignored?
12. post #207584 - 0 results. Previous test without character tag.
13. post #1146671 - 23 results. Gentags only, over 45. Not zero_pictured. See results section.

What I learned:

• zero_pictured kills it.
• Displayed result count is always 1 higher than actual result count.
• It only seems to care about certain general tags and ignore everything else, though test 11 suggests otherwise.
• There may be a minimum tag requirement for gentags. Too few and it won't work.
• Well-tagged images (>30 tags) are way more likely to be found.
• There may be a priority system in place, ensuring at least one tag is in every result.

Try your favourites again and see if a tag shows up in every result. If it does, post it.

Random shit:

• Gotta love the numbers in the results section:
• Test 7 (lucky 7) with 3 results (good things come in threes).
• Test 7 and 11 next to each other (7-Eleven ).
• Test 11 had 6 results. The 6th prime number is 11 (1,2,3,5,7,11,13).
• Test 13 (Unlucky 13) which had 23 results (23 enigma ).
• 7+11-13 = 5 (Law of Fives)
• 7, 11 and 13 are consecutive prime numbers.