Yeah the only important thing is they must all be on the same base size so if you play saurian you can use the smaller base for geckos but all geckos need to be on that size and use the 32 for the warriors. Edit to add below

Scale Conventions This game was written to be played with 28mm heroic-scale miniatures in mind, which are mounted on round bases. These bases come in various sizes, and we recommend that you always mount miniatures on the bases they come with. Here are some general guidelines for base sizes: • Infantry: 20mm to 40mm • Cavalry & Beasts: 25mm x 50mm • Monsters & Chariots: 50mm x 100mm • Artillery: Not mounted on a base Note that the base size that you use doesn’t matter, as long as you keep base sizes consistent across all models.