i've started a wiki page to organise this a little :
http://www.iris2.de/index.php/Art
also uploaded some terrain screenshots for you.
(and linked to my photo collection which might be useful *grin*)
it's publicly writable, so you can also use it to upload stuff if you want =)
terrain is loaded from original uo data, so i'm afraid it is legally not allowed to use it as a basis for new art.
don't bother doing transitions for now, i'll blend them by using multitexturing and automatically generated alpha maps later.
for terrain i also plan on implementing spanning textures, so they can be really high-res like 1024x1024 or even 2048x2048
also please don't bother with water too much, we'll use a nice pixel shader for that later.
the thing you posted is probably a tree-foilage texture,
you won't find the terrain-textures in the iris data directory, it's loaded from texmaps.mul, if you want to see it directly you can use a varans mulpatcher (
http://varan.uodev.de/) or other tools for editing/viewing original uo data.
have you tried installing and running iris ?
i think its hard trying to make textures when you cannot try them out yourself, and it's rather easy to replace the textures in iris and test your new ones directly.
you don't even need a server, you can fly around the world in offline mode also.