1. Is it safe to include images of each mod or CC in your mods folder? Will this slow down the game or bjork it in any way?

2. Coming from TS2 where everything runs the risk or corruption, is there a list of things not to do in the TS4 that might cause corruption?

1. You mean .jpg or .png image files inside your mods folder? I've never done that before with any The Sims games.
2. Nothing I know of. A few things that could slow your game down in a long run if you check in higher number or unlimited sims in edit world mode and your current save files become huge (not sure what the limit size as for today).

Whelp, been too long since I've played The Sims 4 since earlier 2022. I switched all my Sims games to Mac and couldn't afford to purchase Sims 4 packs yet. The base game is rather too dull.

Adding other files, or even other types of folders, to the mods folder does not affect the game. But it may still slow down loading time because the game has to read--and then overlook--those files and folders, too. If you use Twistedmexi's Better Exceptions mod, it will always flag those files and folders as potential problems.

TS4 game will only search for .package files or s4script files, it shouldn't have almost from little to effect if you do so, and at least good news for TS4 has the least corruption involved, you can completely delete unwanted sims even with current marriages, family-ties and relationships without corrupting your save game file unlike TS2.