Cut the cheddar and gouda into bite-size cubes or thin slices and place them in two separate piles on a large round board.
Fan the pepperoni slices in overlapping circles to form a large pumpkin shape in the center, leaving space at the top for the stem.
Slice two black olives in half and arrange them as eyes on the pepperoni pumpkin. Use two more olives cut into thin strips to form a jagged mouth.
Break one pretzel rod in half and set the pieces at the top of the pepperoni to create the pumpkin stem.
Fill the remaining spaces with the mixed nuts, roasted pumpkin seeds, round crackers, and small clusters of red grapes.
Serve the board at room temperature so the cheeses soften slightly and the flavors come through clearly.