If anyone is still looking for a quick and simple solution on how to decode / convert the pictures, I wrote a small cmd file for myself, using the tools freely available on the net. Maybe you find this useful, please see the included readme. You don't have to decrypt the saves, just copy them from your usb drive and let the utilities do the rest. The images are converted to png for easy use.
I tested it with the European version of DOA5 and I have word, that it also works with DOA5U and the US version. If you have any questions, feel free to contact me, though I might be too busy to reply.
You can find it here https://app.box.com/s/tpqmn9uun2gfliuz6wn5
Does it compress them at all? They should be like 4mb BMP files when converted...the last converter I used made them all crap jpg's and there's no way to not have them compressed with that one.
The Dead Or Alive Album saves are some kind of bitmap files with 1280 x 720 x 4 (R, G, B, Alpha) = 3686400 bytes in size. (+ a small header) They are converted to .tga files with the alpha channel stripped, resulting in about 2,7mb files. In the last step they are compressed to .png (a lossless fileformat) and end up typically at 1mb or less in size.
Except for the useless alpha channel, not a single pixel is lost in the process. There is a lossless jpeg format aswell, but I assume your last converter / facebook uploader used a lossy jpeg compression with nasty artefacts. This said, you could stop my script in the middle by removing the commands and go with the .tga file, but I don't see why you would want to do that.