Once you have a good idea how scales work against a chord progression, you should also experiment with moving things around chromatically (i.e: 1 semitone up or down). You can get some great effects with this concept, creating strong dissonance, and then a nice resolution.
If you are improvising in C minor pentatonic, with the notes C, E♭, F, G, B♭, C, then a chromatic movement up one semitone gives the notes C#, E, F#, G#, B, C#.
If you follow the same patterns, and shift up one semitone or down one semitone, you can get a very "out" sound, which is most effective when used sparingly, and with a shift from the root key (in this case C minor) to a neighbouring chromatic key (here C# minor or perhaps B minor), then a resolution back to the root key.
This approach allows for very interesting thematic development, and creates a tension and release for the listener which will keep "static" or repetitive progressions interesting if used appropriately.
The chords of a blues progression can be extended. In a C minor blues, the C minor chord (C, E♭, G) could comfortably be substituted for a Cmin7 chord (C, E♭, G, B♭) or extended as a Cmin9 chord (C, E♭, G, B♭, D ), a Cmin 11 chord, or a Cmin13 chord. Many of the scales and passing chromatic notes will work against these chords, but stringing a melody at speed requires serious study.
When composer, saxophonist and jazz legend John Coltrane began rewriting the rules of jazz harmony by extending chords and approaches to changes, pianists like Tommy Flanagan, Wynton Kelly, and McCoy Tyner were prompted to try to vamp in a way that would compliment such an extensive melodic range.
These extensions are hard to follow at speed, and one of the ways to compensate is to sometimes set aside a strictly chordal approach in favour of stacked intervals.
For example, Instead of playing a Cmin7 (C, E♭, G, B♭), one can stack notes in intervals of 4ths, eg; C, F, B♭. Because there is no 3rd or 7th, there is no clear relationship to a chordal harmony.
These stacked intervals can be shifted chromatically, for example, C, F, B♭ can move down a semitone to B, E, A, or up a semitone to C#, F#, B. Again - used sparingly - this can be used to create a tension and release similar to the chromatic movement of scales, but more open as there is no 3rd or 7th. This also gives you the foundation to play around with moving melodic ideas chromatically.
Stacked 4ths are very common, and can be heard a lot in McCoy Tyner's playing. Other intervals are possible - stacked 5ths will be the same as stacked 4ths, 6ths are interesting. 9ths are possible too.