We've just released the following improvements for the drawings feature of Google Docs:

- Export your drawing as a PNG, SVG, or PDF file by clicking 'Edit' > 'Export' from within the drawings editor

- Add dashed lines and hollow arrowheads (these options will be available in the drawings toolbar once you've inserted and selected any shape, line, arrow or scribble)

- CTRL+G and CTRL+SHIFT+G added as shortcuts for group/ungroup

Thanks for the feedback!
Steve