Urza's Tower, Urza's Power Plant, and Urza's Mine have been a staple in Modern forever, thanks to their ability to let you curve out into a Karn Liberated on turn 3
As someone who has built Elsha in the past, I have to say it ran a lot better with more ways to shuffle the deck when you didnt like what was on top
Ouroboroid This 1/3 Plant Wurm might not look like much until combat begins and your entire board sprouts like it drank Miracle-Gro concentrate
Horizon of Progress is usually going to be able to tap for mana of the colors you need, and it even lets you put lands into play from your hand at instant speed
I suspect it can find a home in Standard decks, especially with many manlands around
Being able to bring back cards like Dockside Extortionist with excellent enters-the-battlefield abilities on each of your turns can be quite strong