What are some alternatives?
When comparing Illustrio and Vectr, you can also consider the following products
Evie by unDraw - MIT licensed illustrations for your next project
Inkscape - Inkscape is a free, open source professional vector graphics editor for Windows, Mac OS X and Linux.
DrawKit - MIT licensed SVG illustrations, in 2 styles
Sketch - Professional digital design for Mac.
Flaticon - A database of free vector icons.
Adobe Illustrator CC - Adobe Illustrator CC is a commercial vector graphics editor.