Is there a way to have K2 automatically add an image if no image is selected when adding an item?

It may be easier to do this by using a k2 template and adding an "else" to display a standard image if the item doesnt have one.
see attached block of code that displays the item view

I will try to make this work, but I use item images throughout the website in different sizes. Check out www.animekyun.com (R-rated).

I don't know how effective this would be. I could technically implement this in every template, but is there a faster way?

I also don't know how to actually make this work. I like tinkering with php so i'll try my best to work this out.

The different image sizes will definitely complicate things. I was only suggesting displaying a stock standard size image if the k2 item does not have one.
The only other way i can think of would be to add the stock standard size image to each item as you go and then you could pick what size you want without difficulty in the item view parameters.
Be sure to tinker in the k2 sub template item view so as not to crash somthing