For that matrix, I used a 35*35 matrix I think. I think the whole island was maybe 8000*8000 pixels, Im not sure. With a smaller size, there is less a break between water and land.
I used Van-B's Van-TRANS to blend the textures for the ED tech island, so there is a smooth transition between land and sand. The link is right here
http://www.andrewvanbeck.btinternet.co.uk/VANtrans.htm
About the other textures, you just need to find a tileable texture. Many come with Dark Basic. The lines showing, thats a bug in PRO.
RPGamer
Current Project: Eternal Destiny
Tech Demo - Colan Island: Currently 716 Lines