You know my experience tells me that relish is very forgiving and as long as you use vinegar and process in a hot water bath you can be very creative.
I've done green tomato, jalapeno, onion and bellpepper with sugar, vinegar and spices that came out wonderfully. Use it on any kind of meat or sandwich.
I've also used zucks, red tomato and jalapeno with sugar and vinegar. Good on burgers
I've canned Jalapenos in vinegar and while a great hot vinegar sauce the peppers where kind of mushy but it's great with red beans and rice. What kind of relish do you want to make? I think the biggest decision to make is how sweet do you want it to be, everything else is kind of determined by what you have available.
My basic procedure is to chop all ingredients to about the same size. I remove the seeds in the Jalapenos but you may like to leave a few if you want a bit of kick to it. Add white vinegar, sugar and a bag of your favorite spices (celery seed, mustard seed, pickling spice if you like) and bring to a low boil for 5 minutes. Place in hot, sterile jars, add a 1/2 teaspoon of fine chopped garlic to each jar, add salt, cap and process in boiling water 30 minutes.
You may want to check with published recipes or the USDA guidelines for exact recipes just to be safe. I have a horrible habit of making use of what I have on hand so I normally read the recipe, get some ideas and then go from there.
Using this recipe as a base I added the jalapeno and used white vinegar instead of cider.