I don't normally do promos but
Here's some people I think you should follow:
Endless Ecdysis - if you like nature, art, and awesome pictures, you'll like this blog.
Uuurben-disasterrr - run by a landscape architect student, she posts a lot of cool stuff, some nature related, some architectural stuff, all around good tumblr.
Sonorensis - another blog geared towards nature, it's definitely worth a follow, especially if you like great photos.
Shot from the Pit - this is one of my best friends photo blogs, she's a great artist and has amazing pictures!
Illuminations in the Key of Dark - primarily an art blog, this is another one of my friends who is always posting awesome work, including some of her own amazing stuff!
And some old favorites:
Sage Tails - Sage is a Weimaraner, and this is her tumblr, she's very nice and very friendly.
Watch Me Paint the Rain - this is a personal blog, ran by an amazing girl named Jess, she's my pen pal, and always open to talking!
RandomKige - this is my sister's personal blog, she's an amazing artist, an amazing person, and runs an all around awesome blog.
Jnetlaughs - if you ever need someone to talk to, Jeanette is the person to go to, she's another amazing person I happen to know in real life, and one of the nicest people you'll ever meet.