Three Underground Seas were too many, and one should have been another fetch or basic
For example, if your commander has the ability to gain a lot of life, you might build a Commander deck with cards that benefit from maintaining as high a life total as possible, and focus on out-enduring your foes - or you might use your life total as a resource, burning through it to fuel powerful abilities and relying on your commander to keep yourself from succumbing
Not counting your opponents graveyard is certainly a downside, but costing half the mana is a big enough upside to make up for this
Land Enchantment - Saga Urza's Land (CTRL to add secondary) Planeswalker Tezzeret, Cruel Captain Whenever an artifact you control enters, put a loyalty counter on Tezzeret
Mouse Armor might be one of the most underrated cards right now - you heard it here first
There are some flashy cards in Iconic Masters