My toddler grew up into a child and ended up with a really ugly outfit. I bought her a better one but I can't stand the fact that she's still wearing the ugly clothes in her character thumbnail. Is there anyway I can reset the thumbnail so she's wearing the new outfit I bought for her in the thumbnail?

If you do change appearance in a mirror it should change her outfit in the thumbnail. You could click on a different hairstyle and then back to the original one just to make sure it thinks something has changed, but it's always worked for me either way.

Right, the 'change appearance' option in a mirror will reset the character pic to the current 'everyday' clothes. If you have the EP installed, it also changes the sim's expression and picture angle.

Uhm,.. you guys dont seem to understand. the thumbs are taken only during an age transition and aren't remade if you simply change outfits.

All thunbs are stored here:
C:\Documents and Settings\(your Acount Name)\My Documents\EA Games\The Sims 2\Thumbnails\

you can safely delete ALL package files from here and they will all be remade the next time you start up the game. It will take a bit longer for that new startup as it has to make the thumbs all from scratch, but as the game often buggers thumbs it's worth doing now and again.

I do understand - I've changed my sims thumbnail any number of times just by changing their clothes and then using the mirror.

Maybe im misunderstanding, but im referring to the picture of the sim that appears over the age indicator in the UI - it DEFINITELY changes when you alter their appearance or change clothes. Even the sim portraits on the left-hand side of the screen change.

Naw you can just use a mirror and it'll update it just fine.