Hello!

I've been trying to find some tutorials/help about doing custom eyes for the game, but it's terribly hard I must say, and I couldn't figure it out by myself.
I also want to ask for a very detailed tutorial(and it should use Photoshop, not Gimp). I don't even know where to start now (-after downloading dds plug-ings and mipmaps).

Can anyone help me with this, please? I'd be extremely thankful!

There are plenty of tutorials around, including some videos. Is there a specific tutorial you're having trouble with?

Basically, you're replacing the eye overlay in the game. You're not messing around with meshing; it's just textures you'll be working with. You want to clone an EA eye so that it has its own instance number, which is a sort of identifier number. If your eyes that you make has the same instance number as any of the ones in the game, you'll be making a default replacement. I'm assuming you don't want to do that, that you want to make standalone eye colors, right? Then you'll need to clone an EA eye.

In a nutshell, you are going to use S3OC or TSR Workshop to clone an EA eye, then replace the image in the EA texture file with your own image using Photoshop or GIMP. Then you save it in Photoshop (or GIMP) in either DXT5, if your texture file has an alpha layer, or DST1 if there is no alpha. Whether or not the texture has an alpha depends on whether the EA texture has an alpha, I think. I've never made custom eyes before so don't quote me on that. But I've done plenty of recolors and the basic principle is the same, I believe.

You'll need a plugin for Photoshop so it can work with DDS files.

Once you're done making your texture, you're going to plug that new texture into TSR Workshop. (You could probably use S3PE for this, but I'm not sure as I don't use S3PE for this kind of thing. I use it to merge my custom content and sometimes to open up a file and look at its thumbnail if I want to identify a file). After you've put your texture into TSR Workshop then you're going to save the whole thing as either a .package file or a .sims3pack file.

This is the basics. I'd use a tutorial to help you with the complete steps, however.

Again, are you having trouble with a particular tutorial?

Yes, you can use S3PE to edit a texture. You can also use Texture Tweaker. I've never done eyes, but I've done lots of paintings. And bookshelves. And a sink that looks like preschoolers were washing their fingerpaint off their hands. And a hair that I've since gotten rid of that was supposed to look like someone was painting pictures in lemon juice on it, but didn't come out right.