Ok Mogura,
here is the current texture:

& I\'m not sure if this is what you meant but here is a screenshot of the UVW Map:
Smaller Eyes:

Big Eye:

(Yellow is un-used texture :] )
I figure that if you make it for the Big Eye the smaller ones will be good, the texture overlaps on the sides, the size of the image really does not matter.
I suggest using the Big Eye UVMap image as a background layer & paint over it or have it be a semi-transparent top layer or something...
& actually this may make it easier, you could just do a cross-section that looks like this:

I can re-size the uv map later...

I put together this texture in like 30 seconds so that is why it is so bad lol...