Can't see as it's inaccessible to guests
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In general those sizes are controled by a combination of the "CSS Settings" and "Thumb Settings" in the Photoplog pane of the vBulletin ACP. Have you tried adjusting those? Specifically, set the thumbs to the largest size you want to display that general size range, and then use the CSS "width: **px;" value to shrink the thumb to the exact size you want for things like the tiny images used in the vB search results.
Hope that helps? Obviously Morgan's the expert, but if you haven't been playing with those two settings that's where I'd start...
James and Susan