Let's take this little old aardvark from here, because everyone wants one in their dungeon.
- clean the shadow up
- use the paint bucket to surround it with a distinctive color
- select that color
- invert selection
- use the paint bucket to fill the resulting hole with black
- invert selection and delete your distinctive color
- save as a png
You can go to the View menu to zoom in. Then select your little guy and go to the Path menu and select Trace Bitmap. It will bring up this wonderfully confusing thing here:
You can move that to the side to see how it looks. If it passes muster, select the old image and delete it:
Now you will have an svg that you can import into Gimp any time you need a non-vector, or raster, version of the image-- like in Blogger or LibreOffice. Click on the svg and open it in Gimp and you'll get a dialog that looks like this:
So, from what I understand, 300 DPI is the highest resolution that will make any difference on the printed page, so if you aren't working digitally, no reason to go higher than that. Whatever number you decide on, put it in the Resolution box. Then pick the size you want in width and height. And it will make an image that you can edit or just save as a png. Ours came out like this:
Now, I want to go back to Inkscape for a bit. This is in case you have a pretty smooth silhouette already and tracing it is making it look too computery. What I've found to work okay, is to leave the default Brightness Cutoff selected but lower that threshold to something like .05.
More importantly, click that Options tab:
and unselect Smooth Corners and Optimize Paths. That should trace almost exactly what you have in your original image.
On the other hand, you may want something a lot smoother. If so, once you've traced your svg, with it selected, go to the Path menu and select Simplify.
That will basically remove data points from the line of your image. I used this to get the slippery smooth snake in my last post. But after hitting it three times in a row, poor Victor looks like this:
I hope that is helpful. I know people make a living doing this stuff and know tons more, but this is enough to let you make some cool handouts and DM aids. If you have any questions ask them in the comments. I'll do my best to answer or maybe someone more knowledgeable can.