Off the top of my head I can recommend the Colloquoy of Aelfric Bata, a schoolbook from Anglo-Saxon England which has a few insults in Latin, though whether these were common is another question.

The Edda by Snorri Sturluson, a mythical and literary technique compendium from Iceland, contains a few stories with Old Norse insults used by the characters. Again, no attestation of these insults used in action, but they're certainly mediaeval insults.

Okay, this is technically sixteenth century. But he would have grown up at the end of the Middle Ages; that was the context for his intellectual development.

Allow me to introduce you to the Luther Insult Generator.

All examples pulled from the great doctor's own writing, and cited accordingly.