Is there a way to change the default photos used for:
1) Moods?
2) Friend-locked entries? (Normally this image: )

Thanks in advance

Unfortunately, neither of those things has a class assigned to it, so unless you have a Paid account, you won't be able to change those things. :(

So something like this would require a paid account?

(custom mood photo)

Yesma'am.

actually, no. well, sort of. You need to switch to a plus account temporarily too add a mood theme, which is explained here

and you can code for all icons, such as the lj-user icon or the friends-lock icon using css in any S2 style. (I assume).

The user icon possibly, but not the lock - there's no class assigned to it, and there's no class assigned specifically to protected entries. Since the user icon is assigned the class "ljuser", the image can be hidden and then replaced with a background image, but if you were to try to replace the lock, the best you'd get is changing every single entry on the page to have that image, even public entries.

The Plus account thing makes sense, seeing as how Plus accounts have many of the same features as Paid accounts, but I was unaware that the mood theme would stay if you were to revert back to basic. I wonder how long it will be before LJ decides to fix this.

in S2 you can change all the images separately - there is a class assigned to each icon.

I pulled this from my own code (though I didn't make it)

obviously you would replace the image with your own

Ah, I see - that's not a class, but it calls the specific image based on its URL rather than a defined class. I tested it, and it works in S1 as well. Crazy CSS tricks these kids are coming up with these days.

You don't learn these things when you're coding actual sites, because you don't have to break the page in order to get it to look the way you want it to. xD