These are .RAW texture files for use with PalMod. You can load them using the File :: Load Texture option in the Preview window. The "Flipped" version is for old versions of PalMod. Current PalMod (1.73 and newer) uses right-side-up RAW files, so "PalMod1.22Previews.rar" will work great with that.
There's a guide on the main site for making your own previews if you want to do that.
Name Last modified Size Description
Parent Directory - ExtraSettings.rar 2020-06-11 15:15 1.0K pointless settings PalMod1.22FlippedPre..> 2021-09-09 21:27 1.0M Old previews (flipped) PalMod1.22Previews.rar 2021-09-09 21:27 1.0M Old previews palmod_eidrian.zip 2020-02-11 23:18 18M MvC2 dev sprites sample-textures.rar 2021-09-09 11:47 32K A few sprites