Since May 2006, the Inkscape and Gimp source files for ELER are available in the source directory at http://geekz.co.uk/eler-source/
The files are compressed with the 7zip archiver to minimize bandwidth.
Each pane is drawn in Gimp without any speech bubbles or text. Heavy use of layer masks is used to cut things out and blend them in place.
The heads are usually on separate layers from the bodies. Most layers have a useful name so you can tell what it is, but sometimes they may be rather cryptic. Get your code wheel out.
When finished, each layer is usually saved in flattened form to a png file, with the name p1.png for pane 1 and so on. This is then used in Inkscape. These flattened panes are not distributed.
Some panes are so similar (just eyebrow movements or something) that I don't bother distributing them.
The strips are now laid out in Inkscape. Each flattened gimp pane is linked into the Inkscape svg file. Bubbles and lettering are added and the whole inkscape page exported to a bitmap.
The flattened panes are not distributed so the Inkscape files will be broken. Flatten the Gimp panes out to p1.png, p2.png etc. and relink them into the Inscape files. Inkscape seems to use absolute file paths, so you'll need to relink anyway. The easiest way I've found to do this so far is just open the SVG file up in a text editor and search and replace the file paths. Easy!
I'll likely make some of the older strips available too. Before May 2006, ELER was entirely done in The Gimp. Each pane was made as before but with the bubbles and lettering too. Then each flattened pane png was imported into a new Gimp file and laid out there.
This prevented me from having speech bubbles leave the confines of their own pane and led to less clearer font rendering.