everything i can think of for targeting biceps requires something, besides your body and the ground.
Pullups are quite simple, as far as equipment, you can find anything to hang onto. good for back and biceps. A great compound exercise
Besides that, just lifting heavy things, or perhaps an isometric exercise, where you pull up like a biceps curl but on something that can't be moved, like a railing or even a rope looped under your feet. Don't mess up your back by pulling too hard.
Resistance bands are relatively cheap and versatile and can be used for curls.