Best success: A full set of high resolution character images from the PC version of Dynasty Warriors 4. I uploaded them to a gallery, or you can download the 25.03 MB zipfile. All are stored uncompressed as common BMP, JPG, and PNG, and thus were easily ripped by Jaeder Naub with their transparency intact.
Runners-up: A variety of partial image dumps done with a TIM2 extractor and converter. The extraction process loses the transparency around the edges of the character portraits and such, and some of the images were not extracted because they reside in compressed data blocks. There's a fair amount of overlap between the DW5 collections because Empires contains a bunch of leftover data from XL, and I couldn't be arsed to sort it all out. Don't mind the lazy.
Dynasty Warriors 4: Empires (28.01 MB)
Dynasty Warriors 5: Xtreme Legends (11.38 MB)
Dynasty Warriors 5: Empires (13.61 MB)
Warriors Orochi 2 (1.8 MB), featuring all those happy/sad/angry faces you see in battle.
Worst frustration: Trying to get at the loltastic expressions in Jan Sangoku Musou - Dynasty Warriors Mahjong. The images seem to be regular old TIM2's, but they're all bundled up in some form of compression that has baffled my attempts to deflate it. If anyone well-versed in Lempel-Ziv variants wants to know what I've seen so far, I'll spill. Otherwise, I think I've put you all to sleep enough for one night.
Honorable mention: Dynasty Warriors 5: Special. Since this is a PC game, I thought it would be as straightforward as DW4. Famous last words. Compression and unknown image formats galore. FAIL
Special thanks to: This info repository, which helped me figure out the structure of the .idx files to KOEI game data dumps. QuickBMS, which allows binary files to be easily processed via basic scripting. Thanks to these, I have a collection of compressed data chunks that I will hopefully be able to decode someday. It's some sort of progress, and I learned something along the way. Hooray?