Museum Souvenir (1/4)
After opening the second gate, take the little path to the left. This leads to the first souvenir.
Legendary Treasure: Geode Glider
At the top of Gift Boat Row is a dual Magic/Life Elemental Gate. Create a Swap Force character with these properties (or use appropriate Skylanders, if you're playing co-op) to open it. Complete the course inside to obtain this.
Museum Souvenir (2/4)
Once you encounter the Loose Cannons, look to your right. You can hop onto some ice back here, then hop across a series of platforms to reach the second souvenir.
Museum Souvenir (3/4)
After exiting the Ticket Taker to the upper level up Paleo Pass, move toward the pair of rocks. Destroy the crate and follow the short path to grab this.
Story Scroll: Frozen Galleries
A little further ahead, you'll encounter two huts. Cross the bridge into the smaller hut. Inside, you are tasked with defeating all the enemies in one minute. If you do so, you'll open the Battle Gate and reveal this.
Museum Souvenir (4/4)
When you reach Glacial Galley, take a left by the flaming bridge. Head south near the Earth Elemental Gate to spot some platforms you can jump to. Cross them to find this on any icy ledge.
Hop back across the platforms to the Earth Elemental Gate. Use an Earth Skylander to open the way, and head inside. Rotate the center platform to access either Battle Gate. Take out the baddies to unlock both, and grab the keys inside. With both keys in hand, you can open the gate in the middle of the area and claim this.