It's absolutely crazy that you can only have ONE object in the scatter brush or symbol sprayer. It's such a basic feature that shouldn't take long to implement, but would be SO helpful for creating randomized stuff in your work. We need this ASAP.

A related request:
Select multiple symbols for Symbol Sprayer
http://illustrator.uservoice.com/forums/333657/suggestions/48787379

We have two plugin solutions to deal with it:
1. Live Symbol Path effect from CValley FILTERiT suite: https://www.cvalley.com/products/filterit5-2/
2. Symbol Stipple effect for Astute Graphics: https://astutegraphics.com/plugins/stipplism

This request is somewhat related to that one:
Paste / repeat symbols / objects along a path
http://illustrator.uservoice.com/forums/333657/suggestions/41707711

This would be so useful

I would also like to see this feature. It would be great when creating a continuous pattern brush based on something like a pencil stroke. Only being able to use the one repeating section takes away some of the authenticity. Having the option to create multiple variations that show up at random intervals would help create a more natural look for these types of brushes.

Pretty much like the existing scatter brush, but with the capability of using multiple different images. A slider could allow for adjustment of the frequency and randomness of individual images.

At the moment scatter brushes can only repeat one element, and pattern brushes can only repeat one kind of side tile.

I want to be able to make brushes that are made of multiple different symbols scattered along the line. Ideally different probabilities for each symbol, or random spacing between them etc.

Let's say I want to create a line that has several different daisies scattered along it. At the moment, I could make my daisies, but I would have to group them then create a pattern or scatter brush from the group. As a result, the brush repeated the group and the daisies always have the same relationship to one another.

What I would like to do instead is be able to add each daisy individually to a brush, and have different settings for each, so that they are differently distributed along the path.

You can add second stroke and apply you other brush to it.

I hope this feature gets added! This would be super helpful for my team. It would be a great add to the tool—and help save some time too.