For our project, we primarily work with corpus data, but we also have funding to do further field work and elicit contexts that are rare or unattested in the corpora. As our primary method of elicitation, we have decided to use storyboards, which are short scripts accompanied by pictures.
I have created the pictures for our stories in Inkscape. The stories and SVG source files are being made available on our project wiki. The SVG files can simply be customised, just credit the project and me with the original creation.
However, the options for customisation are limited. I use the free and open command-line tool GMT for the production of linguistic maps. It has awesome tools for all kinds of tasks, including the mapping of symbols from a file of coordinates. Here is a quick guide on how to produce your own pretty WALS map.
Download your data set from WALS in tab-separated values (there is a button just underneath the header). Save it as walsXY.xy, where XY is the WALS feature you want to map.
Remove the metadata lines at the top of the file and the header of the table.
GMT does not distinguish between tabs and other simple blanks. Replace all simple space characters by nothing or a character of your choice.
Start GMT and move to the directory to which you have downloaded your data set and where you want to produce your map.
In the same folder, create a cpt file containing the colors that you want to assign to different values. My wals.cpt file has the following content: (number of WALS value, RGB values).