Well MTG Forge seems to have as many flies as Aunt May's pie on a hot, summer afternoon. Downloading the card pictures has caused a few problems to surface. If MTG Forge can't read a link (url) it presumes that you aren't connected to the Internet. MTG Forge doesn't take into account that the link might be dead and like Abraham Lincoln, I cannot tell a lie, I wrote the buggy card picture download code.
You can just download a new file, "card-pictures.txt" from here.
The whole program, MTG Forge, with the fix can be download here.
And here is a link to those wonderful, full-frame Zendikar basic lands. Just unzip them in the /pics/ directory and overwrite the old land pictures.
All 20 Zendikar Basic Lands
p.s. The new user interface "jumps" some and you can prevent that by resizing any of the panels, such as the two "card detail" panels on the right. I hope that makes sense.
p.s. And if downloading all of the pictures in one big file is easier for you, here are these links.
All Card Pictures (47 MB)
New Card Pictures (1.3 MB) - Includes only the 40 new cards pictures.