Hey I was just wondering how to make new textures for creatures?

I made a new .dds file for a mr handy but when I go into the geck I can only choose from the pre determined mrhandy/gutsy textures and models.
This appears to be the case for all creatures.

Just wondering how exactly I'd go about changing this so I can use my own creature textures, thanks =)

There is a great compiled guide by Miax:
http://www.fallout3nexus.com/downloads/file.php?id=6107

To summarize:
You need to download utilities called Fallout Mod Manager (BSA browser is included) and Nifskope.

1) Extract mrhandy model (mesh) from your Data/Meshes.bsa (it is in hierarchy "meshes\creatures\mistergutsy\misterhandy.nif"
2) Copy misterhandy.nif to "newMrHandy.nif"
3) Open newMrHandy.nif with NifSkope. If you have not extracted the original textures from Textures.bsa it will show only wireframe.
4) Explore the model hierarchy tree until you find a node/line called BSShaderTextureSet, there could be multiple, so check them all. In block details (the lower window section) expand the Textures node. There you should see the Textures. With right mouse click select "Texture > Choose" and then browse you own texture.dds file. Now you should see your custom texture.
5) Save

6) In Geck you have Creature objects like MrHandy. Edit and make a "NewMrHandy"
7) In that object you can define the 3D model file for that MrHandy. Browse and select your newMrHandy.nif. Close object windows and drag & drop in to render window

Hope this helps!
--
Mikkis
p.s.
Now if only some smart guy could help me with getting my vault suit normal map working