Effects pedals, like the ones shown in the photo, are great to use on any instrument in any application. This certainly is not news and certainly is not a new idea, but I am continually surprised when I get reactions from people that say "your using that guitar effect on your synth? I never thought about doing that!".
There are many unconventional ways to use effects that give very nice, interesting results.
Here are a few examples:
1 - feed the output of a filter through a distortion box, then back into the input of the filter again (distortion box in the feedback path). Depending on the amount of distortion and the type of filter, this can range from a subtle change of the filter characteristic to a warm fuzz effect to raspy distortion. If the filter has multimode outputs, experiment with using one type of filter for feedback while listening to a different filter output. Another option is to put a phasor in the feedback path. Again, one can experiment with multiple filter outputs through multiple effects, all mixing back into the filter.
2 - send your sound through reverb, then through the distortion (most multi-effects boxes unfortunately have this chain backwards - they distort, then add reverb).
3 - send a sound through mulitple phasors - at least 2 or 3, all at different rates. This is especially nice if the phasor pedals are different models - for instance, an EH Small Stone into an MXR Phase100 into DOD Phasor. Unless you feed back any of the signals and mix it in with an input of one of the pedals, order of these effects should not matter.
4 - try to trick devices that are meant to process a single frequency by giving them chords or clusters of tones. One of my favorite pedals to use in this way is the EH (electroharmonix) Octave Multiplexer. The EML Polybox (see my other post) can be used in this way as well.