Larger header logo size

This is possible, you will just need to follow some instructions below to make this happen. First head to the "Edit Theme" section, scroll down the left hand sidebar till you reach the bottom of the page and click "Advanced Options". On the next page you will see a code input field titled "ADD CUSTOM CSS". You will need to copy/paste the code below into this section and click "Save" when done.

.portrait, .logo {width: 350px !important; height: 350px !important; max-width: initial !important; max-height: initial !important;}