first, several times i have left coffee brewing in its little jar on the counter and forgotten about it until the next day. turns out, if you let it cold-brew at room temperature for 24 hours and then put it in the fridge and then filter it later (a few hours or days - it doesn't seem to matter much - the coffee just gets a little stronger the longer it brews), it is perhaps even better - i think the flavors get more nuanced - maybe even more kind of caramel and vanilla and chocolate-y.
second, light coconut milk is delicious in iced coffee. i've been using some coconut milk and some regular milk, but if you super-like coconut and like somewhat viscous drinks (pleasantly so, but still), maybe you should try it with just coconut milk. since coconut milk comes in cans and it's sort of gross to leave stuff in cans in the fridge (isn't it? am i just too squeamish here?) i open a can and pour it into an old jar to store - one can lasts a week or so in daily coffees.
finally, and this will certainly have occurred to the more astute coffee connoisseurs out there already, sweetened condensed milk. yesssssss. vietnamesify that coffee, son! this is to taste, because i usually don't sweeten my coffee at all, but a little condensed milk stirred into cold coffee on a hot summer afternoon never hurt anyone. even if it did, it was probably worth it.
one final note* - if you want to bring cold-brewed coffee to work with you and you don't have a fancy cup with a lid that keeps liquids in, you can put it in a jar and drop the jar into an enormous wool sock - the sock will insulate the jar and keep your coffee cold. it will also help to ensure that coffee doesn't flood your bag.
*final note may only be applicable to my own situation and collection of capacious wool socks.