When practicing improvising it can be helpful to have something to play with. A practice partner is great but if you don't want to drive them crazy as you work out licks a backing track is probably better.
Thankfully we have the internet. Head over to YouTube and do a search for "backing track" to find a long list of tracks to practice with.
Even better, narrow down your search like I did recently with "blues backing track in d major". I found this one I liked: Blues Backing Track in D Major
Another a little more soulful I am using slide with is: Slow Soulful Blues Guitar Track in D For this track I am especially trying to work on pauses in the improvisation. As well, I am trying to repeat licks to come up with something that is interesting to listen to.
For a much better example of improvisation and to watch a more detailed discussion of improvising check out Justin Guitar's: Major Scale Pattern 1: Basic Improvisation lesson. This gave me a lot of insight on how to get started.