This photo I snapped approaching a pretty good downpour, it just looks awesome!

These clouds only look nasty, nothing came from this particular system.

These clouds are a good indication of imminent sever weather. They are called Mammatus clouds and often accompany severe thunderstorms though they themselves do not cause sever weather, these clouds are also an indication of a possible tornadic thunderstorm. They can however accompany non-severe thunderstorms at times as well.

This is a non-rotating wall cloud I photographed up close and personal!

Same wall cloud better defined, note the lowered base and the growth of the cloud…this was only a few minutes after the first photo was taken. This wall cloud did indeed begin rotating after passing by me, unfortunately I was working and could not chase it!