The medieval woodcuts in Fanfics, Kelvar and Olvar, and the Intelligence pages are mostly from:

Medieval Woodcuts Clipart Collection
K&O: Mainpage, Behaviour Patterns of Cave Troll, Mordor Thorn, Lichens, Turnkey, Sea of Nurnen, Reginald Barnes.
Fanfics: Mainpage bottom picture.
Picture Credits: Top picture.
Thread Library: Main picture.
Medieval Macabre
K&O: Behaviour Patterns of Common Orc, Fire Lily, Nobody's Legacy.
Intelligence: Mainpage.
Fanfics: Mainpage top picture.
Mudslinging: Mainpage.
Mythical Plants of the Middle Ages
K&O: Sun-Dew, Beach Tree.
Tales of the Middle Ages: Cats
K&O: Swearril.
These sites are all linked, giving lots of great information on medieval life, beliefs and death, and they are superbly illustrated.

The illuminations and transparent woodcuts/line drawings that appear in Kelvar and Olvar come from this site:

Retrokat Medieval Freebies.
K&O: Balrog Body Parts, Behaviour Patterns of Nazgul/Scavenger/Condor/Peacock, Ivee, Flytrap, Dandelions.
Minas Mornie Assault Course: Mainpage.
This is another wonderful collection of medieval art and illustration, well worth exploring if you're looking for borders, banners, etc.

Another great clip art site is:

Lord Kyl's Medieval and Fantasy Clipart
K&O: Behaviour Patterns of Balrogs, Snapdragons, The Grish/Aiw/Sera.
Here you will find hundreds of images. Really good site.

The rather over-sized raccoon image in K&O's "Raccoon" page comes from
Animal Pictures Archive

The three duck-torture photographs in "Duck Soup - Session 2" (Mordor Thread Library) were created by
Vivienne the Poetry Maia.