Hey There. I maintain the WordPress One-Click image. This change was made several months back. The restriction was put in place based on memory requirements but our system only currently restricts creates based on the size of the droplet used to generate the image with the message showing the disk space message (there is a ticket open internally to update this).
We chose to restrict WordPress droplets to the 1GB size because a standard WordPress + LAMP install on a 512MB droplet will, within a week, crash due to MySQL running out of memory.
You can still create a 512MB WordPress droplet.
Copy the script found here.
On the create page, select a 512MB droplet and Ubuntu 14.04 LTS as your operating system.
Check the "user-data" checkbox and paste the script into the box that appears.
Select any other options and click create.
If you plan to launch more droplets like this you can immediately power off the new droplet and create a snapshot image to use for new creates.
To get around MySQL crashing the first thing you'll want to do is to create a swap file on your droplet. These commands will create a 1GB swap file, enable it and set it to be used automatically on reboot:
fallocate -l 1G /swapfile;
chmod 600 /swapfile;
echo "/swapfile none swap sw 0 0" >> /etc/fstab;
I would also recommend using a caching plugin or CDN. Placing CloudFlare's free service in front of your droplet or using an existing caching or CDN wordpress plugin can do this. While a CDN and caching are not absolutely necessary, they should speed up your site's load time and lessen the load if you receive a lot of traffic.
I hope this information will help. We want to make it as easy as possible to create the stack you want to run but continuing to offer a WordPress image for 512MB droplets that was likely to crash if you didn't take further steps to optimize it was not a user-friendly way to do it.
If you have any other questions or run into any problems we're here to help.