Unique armor and texture sets in easy steps
This is me 'payin' it forward'.
For information to get you started in Modding Check out Modding Basics One
DDS Converter is a handy utility for custom textures.
If you'd like to create a non-replacer Re-tex armor it's really easy in the G.E.C.K. I've found people appreciate to have both, a replacer and a non-replacer posted on the same page. There are (at least) two ways to do this, but I'll explain the best and easiest way as it was explained to me.
Using this technique you won't need to upload the meshes associated with your texture.
1) Create a copy of your texture and associated normal map (_n) in a new folder. Title the folder appropriately and place it in Fallout3/data/textures/armor.
2) Launch the GECK and load the Fallout3.esm data file.
3) In the OBJECT window navigate to Miscellaneous/Texture Sets. Right-click, create new. Name your texture set whatever is clever I suggest it begins with a number so it's easy to find later. Highlight 'Diffuse' and click edit at the bottom. Navigate to the new folder you created before and choose your custom texture. Highlight Normal/Gloss and repeat the above step except choose your (_n) normal map file. Click OK and you'll see that your Texture Set has been added to the list.
4) In the OBJECT window navigate to the base armor associated with your texture under items/armor and create a copy. Change the Editor ID to something Unique, I suggest it begins with a number so it's easy to find later.
5) Edit the rest of the fields the way you'd like the armor set-up. Most of it will be filled in already because you copied the default Armor, so just edit the fields you'd like to be different with your Unique armor.
6) This is the important part for your custom texture: Choose 'edit' next to Male Biped Model. The names in the next part change slightly depending on what armor you're editing. You need to change all the fields which don't say MEAT in them. So likely, arms, upper-body, ect. Double-click on any of those pieces to edit. If you titled your Texture set with a number it should appear near the top. Double-click to choose your Texture set in each of the fields which don't say MEAT. Click OK when you're done.
7)Repeat that process for the WORLD MODEL, there should only be one field to change. And the Female Biped model if applicable.
8)Click OK on your armor and SAVE.
9)In the CELL VIEW window, find a cell, or two, or four where you'd like to place the armor. I like to test by adding them to the Women's Bathroom in Megaton (Interiors). Once you have the CELL loaded in the 3D view, drag your armor from the OBJECT menu into the 3D view. Place it where you'd like (you can ctrl+F to drop it on the floor).
10) At this point you should be able to see your armor laying on the floor/wherever and the texture should be yours.
11)Save and exit. You're done!
If you have any questions gimme a shout.
Hope that helps :)