If you have a nice terminal (maybe w/ a pic of something dear to you) and you are running nvim/vim in it, your colorscheme might put a background that covers your terminal. You can easily remove that by
:hi normal guibg=000000
Note, it is not #00000 (that would be the color black, whereas you want transparent, meaning vim does not put anything there so you can just see your terminal).
I do this a lot, thought to share w/ all fellow lovers at AL
PS: Rest of colorscheme will not be affected.
Current vim colorschemes using: codedark, oh-la-la, anokha