On this page you will find a selection of custom flags which you can use in-game, as well as their authors and any notes they would like to include about the artwork. Split countries are combined back into original form; i.e., there is no "West" and "East" Libya. There is also a list of custom flags for coalitions. Open the Table of Contents or use Ctrl+F to find your desired nation. List is in alphabetical order.
There are many nations that don't have any custom flags yet. To add additional flags, all you need to do is go into the edit box for the particular nation (edit link is on the right hand side of the nation's name, further down in the page), right click on the bottom of the table, hover over to Row and then click on Insert Row After, and then fill in all the information.
Chances are that you'll want to add a photo and it won't be in perfect 64x40 pixel dimensions. In such cases where your image is too large, visit this page to upload your photo rather than using the editor's upload tool:
Afterwards when editing the table, instead of dragging or inserting the image into the "Flag" column, simply type out: File:Picturename.jpg|64px, enclosed by double brackets. This will automatically create an internal picture link that is scaled to the uniform size. This way, clicking on the picture will then take you to the larger version of the image, provided it has one. An example of it is;
You can also just use the built in editor's tool and someone like me will come around and fix it later. It's up to your level of technical skill.
Given that many of the nations are interchangeable and that the 30 player map is merely the basic 10 player Europe map expanded to include other nations as well, nations from both maps are amalgamated here.