Never seen any impressive spaceship mats for bryce, i usually use regular image textures 4 it ! :)

Here is couple of links !

Some regular textures:

http://www.davegh.com/blade/davegh.htm

Tutorial:

http://www.brycetech.com/tutor/bryce/spaceship.html

Some of the ships from this page have a nice textures on them, not sure about tems of use, check with authors !

http://www.ultradrive.com/b5_3d_index.htm