First you need to decide if you want this new view to fall under one of the other root views (Audio, Images or Video). If you want it to, then just right click on the root view of your choice and choose "Add Library View..." If you want to create your own root view (which would seem to make sense to me since you're not going to restrict this new view to just one media type or another), then click on Start in the tree, then click on the View menu (up top) and then Add View -> Add Library View
Whichever you chose, on the Add Library View window you now have another choice to make. You can pick one of the stock views here or choose the Empty View option. If you pick a stock view, once you click OK you get your view in the tree and now you have to right click on it and choose "Customize View". If you pick the Empty View option, then you'll just be taken straight to the Customize View box.
Still with me?
Once you are in the Customize View box, in the rightmost Options pane you'll see a grouping called "Advanced". Open that up and you'll see two options of interest. One is a checkbox labeled "Use parent scheme rules for file display" and the other is a button with just "..." on it and the label "Set rules for file display..."
Here's where it gets fun. Click on the "Set rules for file display..." button and you're presented with the same Search wizard you see elsewhere. Just use this to determine which files you want to display (or not to display). The root view of Images would have a rule set that says to only include files whose Media Type is Image. You'll probably want to set a rule that says to include files whose Media Type is Image or Video. You can also set any other rules you want in here. Once you're done, just click OK.
One more step... If you've created this view as a member of one of the 3 main root views (Audio, Images or Video), then you need to clear the checkbox labeled "Use parent scheme rules for file display". What this option does is basically causes this view to inherit any rules that it's parent has. If you created this view under Images, and left this box checked, then you're still only going to get images because what happens is the root view Images is set to only have image files. So then your new view only gets a list of files that are images. So even though it's set to display images and videos, it doesn't have any videos to display. If you uncheck this box, then your view basically ignores whatever comes before it and gets to start over with your entire library.
I hope this makes sense and didn't get too confusing.