Can frozen peaches be made into jam or other things?
You absolutely can make jam from frozen fruit. 

Freezing is like "stopping time" (or at least slowing it down almost to a stop) for the frozen food. Freezing water breaks cell walls, that's why thawed fruit is mushy, but so does boiling when making jam, so no problem at all here. You can also freeze leftover fruit before it spoils and combine various fruits in your jam or make flavour pairings with fruits that are in season at different times.

You can either puree your fruit and freeze it in a ziplock bag or flat container or freeze chunks on a tray, then transfer to bags. Good wrapping is essential, as with all frozen foods. 


Personally, I often freeze puree because a) it needs less freezer space and b) we prefer smooth jam. I pre-meassure one batch and cook the jam when I have time.
Freezing individual pieces, on the other hand, has the benefit that you can choose later how much fruit you need for a recipe. This is also good if you haven't decided about your recipe yet or love to combine flavours. These pieces are also usable for other dishes.


Storing your prepared fruit in the refrigerator is not without risk. Overripe fruit spoils quickly, even in the refrigerator and "later" quickly can become "too late". So unless you are absolutely sure that you will cook them tomorrow and they have no "dubious" (e.g. mushy, about to get moldy) spots, just freeze them.