The most common break to the up/down pattern that I know of is fret-hand muting: rather than fully fretting the strings into contact with the board, relax your fingers so that they rest on the strings. this makes more of a clicking noise when fretted, but quite a few guitarists and strumming styles call for it. You wind up adding two more "sounds" if you will to your possible patterns: just as an up-strum doesn't sound quite the same as a down-strum, so does an up-strum muted not sounds the same as a down-strum muted. It's easy. I'm not the sharpest knife in the drawer, but I actually learned pretty quickly to relax-tense my hand in time to what I was playing.

Actually, maybe the most common way would be to accent a stroke: play slightly harder or louder on an up or down. This, plus fret-hand muting, can give you six minor but distinct "changes" to how you play a chord, from which you can contruct patterns, all without acutally changes the up/down swing.

I think they're called "arrasgeados", where you bunch your fingers in a loose fist over the strings, and then flick them off your thumb across the strings one after the other, it's more of a fingerpicking thing, probably hard to do if you're flatpicking.

Other than that, maybe find pieces of music you like that feature distinct strumming patterns, old school ska, for example, relies a lot on a sounds up-strum and a muted down, flamenco has patterns, a real common swing-jazz pattern is:

down-rest-down-rest-down-up-down-up

A guitar teacher will probably tell you to just practice combinations like these, in different time signatures.

I like the double time strum, the right hand mute, skipped beat and shuffle strum a lot.

Hey Lisa,
Glad to hear your playing. Take your time all good things will come. I've been playing since I was a kid. Love your music no matter how it sounds its your inner -self wanting to let the world hear your music. Your dilema is minor just play slow, fast, hard,soft let it all out. The ups and downs of strumming is a basic problem. Get a metronome and practise to the beat, speed it up and slow it down. Strum twice and let the metronome fill in the silence. Learn to keep the beat and the rhythm will come. Take your time, experiment with your guitar all will be reveled to you if you practise long and hard. Virtuoso we are not,but music lovers we are, so live long and prosper and rock on to your own beat. 1,2,3,4,1,2,3,4,1,2,3,4!.....

Set that Pick down. Ok

NOW STEP AWAY FROM THE PICK !!!!

Ok great. Strumming is - well - it's not going to keep you happy for long. Very quickly you will have outgrown strumming and you will have learned to play that way. The result will be a tougher learning curve to pick up a more satisfying style such as flatpicking or finger picking.

ERGO: start learning finger style now.
Use a thumb and one or two fingers (preferably 2 - 3 fingers ) Try to establish different finger riffs in various chords that use a finger on particular strings. Within a month you will be very impressed with yourself. If you start with one finger add a second within two months, then a third. Never let yourself stagnate.

Then and only then, go find that pick and try flat picking. Listen to Doc Watson. He uses a pick. He's a flat piker.