Illustrations that I have added to Wikimedia Commons and inserted in some articles:
Illustration of the electric field surrounding a positive (red) and a negative (green) charge (click for larger image). I inserted this illustration in the Electric field article.
Illustration of the electric field surrounding two equal charges (click for larger image).
Illustration of the electric field surrounding one positive charge (click for larger image). I'm not quite satisfied with this one, but I don't see any article where it would be obvious to use, so I won't improve it just now.
Wikipedia has keystroke combinations that can speed up your work, like ⇧ Shift+Alt+F to "focus" on (jump to) the search box, ⇧ Shift+Alt+M to move the current page and its talk page, ⇧ Shift+Alt+T to open the current article's talk page, ⇧ Shift+Alt+Y to open a list of your user's contributions, and many more. Those are for Windows users. On the Mac OS, press Control instead of ⇧ Shift+Alt. For some browsers, the accesskey is the Alt key instead. For details see Keyboard shortcuts.