How can I create iPhone screenshots without the lock button? Is there any way to create a screenshot of an iPhone without using the combination home+lock button? Is there an app for jailbroken phones? Something else?

I do not have a Mac; only Windows.
Go to settings>General>Accessibility>Scroll down>AssistiveTouch

Turn it on.

Then you just click the home button and it gives you the option of screenshot if you do this:
Click device>More>Screenshot and you are done!