Being that I am cheap and poor, I use GIMP to edit all of my photos. When I decided that I wanted to give illustrations a go I found Inkscape, which is free like GIMP.
Once I figured out how to use Inkscape I noticed that you can not save files natively in jpeg format. This would be a problem for submission to DT.
No problem. Using GIMP you can convert an Inkscape svg file to a jpeg. Here is how I do it although there may be a better way. If anyone knows a better way, please let me know.
First I always start my projects as desktop_1600x1200. This seems to give me enough room to work and creates a sufficiently large enough image to upload to DT when finished.
Once I finish my work in Inkscape I save the project as an eps file, Encapsulated Postscript. I use PostScript Level 2 and set the dpi to 300. I then use GIMP to open the eps file. Please be aware that Inkscape will not save all of the white area of your project but will only save the objects. I keep my white area by adding a box the size of the project area, giving it a grey color, and moving it to the bottom of the project. Once I get into GIMP I convert the grey background to white. For some reason if you make the box white, Inkscape sill only save the visible objects and leaves out all of the extra white area.
Once I get the eps file open in GIMP, I take once last look at 100%, look for any defects, and use the GIMP tools to fix. Then I save the file as a jpeg and upload to DT. The saved file is 5302x3977.