There is usually plenty of storage for regular sized backpacks. On the other hand, if you're referring to those enormous torso-sized waist hugging backpacks some gap year students carry across Europe and Asia, then it may not fit. Depending on the weight, size, and station services you may be able to check larger bags, or you might have to rearrange things a bit. If bringing an extra large backpack you might want to include a thin collapsible duffel bag to help make it easier to separate and rearrange items as necessary.