Made a bland curry, it's cooled down and about to freeze it. Help!

I have no idea how you're going to reheat your curry, but if we assume it's in a pot over the campfire, you have a few options:

1. Bring spices with you, bloom them in oil, then add your pre-made curry to reheat.

2. Make and cook a spice paste ahead of time (or buy one), as it won't have the 'raw' spice qualities that using a curry powder will. You can then stir it into the curry to taste as you heat it up. If you're using a curry roux, you may need to add a little extra liquid, as it'll act as a thickener.

3. Bring along chutneys, Indian relish, or similar things that people can mix-in to add flavor. (I like the 'hot' chutneys for adding flavor. Sweet chutneys are better for mellowing out a chutney than adding flavor on its own)

4. Serve it over heavily seasoned rice. Dice up some carrots and onions, cook them in oil with a (possibly heavy) pinch of salt, add any spice powders or seeds (tumeric, mustard seeds, whatever else you like in your curry), add the rice, let it toast a little bit like for risotto, then add your liquid and steam as you normally would. I'll sometimes also throw in a cinnamon stick or a few cloves in just before I add the liquid. But count the cloves and warn people, as eating under poor lighting conditions can result in surprises.

I wouldn't suggest reheating your curry in advance; camping typically suggests food storage without refrigeration, and you often have hungry people not waiting for food to fully heat back through. Because of this, it's best not to keep reheating / cooling off food unless you're going to bring it to a full boil each time, and that could start turning the meat and vegetables into mush.

Adding spiced to a cold curry isn't going to do much for you, you need heat to activate them and draw out the flavors. I would take the spices with you and add them once the curry is heated up. Try some Garam Masala and don't forget salt.

Reheat your curry. Add the desired spices until it gives you a satisfactory taste then freeze it for your upcoming camiping trip.

As someone suggested, bloom some spices in oil - you could do this now, in advance, and store the spiced oil (in the fridge or freezer), to mix it in later when reheating. You could also mix the spiced oil in now, before freezing the whole.

Also, you might want to season it with more sugar, salt, and acid (vinegar or lime juice). If this is a vietnamese/thai/chinese/japanese... (as opposed to indian) style curry, also consider adding soy or fish sauce or even MSG.