ManyCam will suit your requirements.. It's free, it covers all the features you've requested for.. Software is really excellent, I've installed on my computer as well (Windows 7 though) but it's supported on Windows 8 as well....
Below are the Features listed for the software..
Use your webcam with many applications simultaneously
Use your webcam with multiple chat applications at the same time. Use
Skype, MSN, and Youtube at the same time with ManyCam's virtual webcam
Add amazing webcam effects & graphics to your videos and photos
Add thousands of amazing webcam effects and custom graphics inside any
webcam application. Change your face, eyes, hair, add backgrounds, and
Switch between different video sources
Quickly switch between video & audio sources with our ManyCam Pro live
video studio switcher. Learn how to live stream with our video
Screencast desktop and draw over video
Draw over your video window or screencast your desktop online with our
software for your webcam
Add amazing microphone audio effects to your broadcast
Try our live audio effects & voice changer. Improve your microphone
audio quality, make a funny high voice, low voice, or disguise your
voice with any app.
Create your own webcam effects.
Create your own custom webcam effects & graphics.
Screenshot from my Computer
Record various screens...
Toggle between Camera and Video
Set the resolution yourself, customize various options..
Bad point about the software - Buy else it will Watermark.
You can also try out CamStudio but there is no screenshot facility here. But rest is pretty good, it's free, it has loads of features as well.
For screenshots you have a great inbuilt functionality in Windows 8 itself.