I've two ideas and both of them are homages:
The first one is inspired in this image, belonging to the last stand of the Crimson fists, in WH40K:
The idea is to show a group of magi and their grogs in a similar situation, with several rows of grogs, armed with different weapons and armor(spears, bows, sword and shield, etc) surrounding and shielding three magi, with the bodies of the fallen and wounded at their feet. Some of the grogs would show magic items, f.e. shining weapons, bows that fire flaming arrows, a grog that is still fighting even with grievous wounds, etc. The magi are also fighting, with the magus to the left raising a giant stone over his head, ready to throw it to the enemy, the magi to the right has just created a fire elemental and the magus at the center is calling the lightning.
The second idea is an homage to the Ars Magica 3rd edition cover. The action is showed from the point of view of the enemy, with a first person view of a group of magi and their grogs charging. At the center of the scene there is a heavily wounded warrior, with sword and shield and full chain mail, maybe a favored grog or even a Ramius Flambeau who is still fighting thanks to his magic items. He is the vanguard of the attack and is flanked by several allied grogs armed in different ways(spears, axes, etc). Behind the vanguard, two magi can be seen, one attacking to the left, is throwing fireballs, meanwhile, the other is attacking to the right with an invoked wolves.
It's important to note that, in no one of both images, the enemy can be ascertained: they could be mundanes, faeries, demons, other magi, etc