Puzzle ramped up to ~8/11 [[All solutions posted]]

So sometime in the last couple of days I've passed 2 years on Steamgifts, so I thought it's a perfect time to do a little giveaway, or 2, or more. Everything you need is down below!

E: Usual Steamgifts rules apply, absolutely no spoilers or passing links.

E: For clarification, you should find 5 letters, in a xxXxx fashion, all are letters and the capital X is a capital letter, other x's are lower-case. But that's not the letters of the giveaway code, there is one more small step.

1st hint: look at everything I've given you.
1.5st hint: look really closely.

2nd hint: you should have found a series of images (not the ones used for the ITH quizzes), there's something hidden in those images.
2.5nd hint: because one of the things you should be looking for might look like it is part of the image, I'll give you this one. It's the letter 'c' on the second image. I'm not (yet) going to tell you where that is.

3rd hint: some people have now found all the letters but are missing something... Look at the ITH quizzes again in depth, especially the first and last ones.

4th hint: what would Caesar do?