When I browse through my downloads folder with the Clean Installer, I can see some items whose "preview" appears blank. Now, I know I've got some bad files mixed in, since I have user-created clothing in-game which makes my Sims' bodies appear invisible if I put them on (this is not the desired behavior). I'm uncertain which items of clothing are at fault, since the thumbnail for each of these items of clothing in the game is the same outfit (I believe it's an outfit that comes with the base game). Is there some innocent reason why these textures don't appear in the Clean Installer's "preview images" screen (they are not meshes)-- or are these likely the offending items of clothing?
The Clean Installer just shows you what is in the package. There could be valid reasons why the preview is blank (do you mean that the preview is completely white?); the Clean Installer has no way of knowing what the pictures for individual CC should look like.
If you are unsure whether to keep something or not, you can always backup your save game, then remove everything except the questionable CC and any related meshes. Run the game and determine whether you want to keep or remove the CC. Then, you can restore your save gane and all of your remaining CC.