Advanced Wallpaper Program

I know how to do this, I've resized a handful of my favorites already but there are hundreds of large images on my drive. I'm not going to sift through and manually resize/crop that many images, especially seeing as I don't know off hand just which pictures I'd like to use.

I'm thinking of a way to do this more on the fly by just browsing my images in an ACDSee type of way, quickly zooming and panning to the portion I'd like to use, then applying what's viewed as wallpaper.
Using image editors like Paint.NET is too cumbersome to do something that could be so simple.

To clarify, I'm not very interested in setting up a wallpaper slideshow. It's more about manually setting specific wallpapers on the fly at my own discretion.

Using an image editor would require zooming and panning until I found what i wanted, resizing to the zoomed setting, cropping the portion I want, saving the image as a separate file (don't want to overwrite originals), then going to that saved file and setting it as my wallpaper.

I would like to eliminate the steps in red and just do the bold steps.

@Howling Wolves, I'm trying to set my wallpaper as specific hand-picked portions of an image without warping/stretching. This isn't something that can be done in batch.

I'm even looking to use several different variously zoomed portions of single images.

Edit: I'd also rather not save each adjustment as an individual image. Maybe a program could just save several zoomed/panned parameters for the images. But that's really getting beyond my main goal on-the-fly-portion-specific walling!

Sorry for catching this thread so late. I have had great success with Faststone Image Viewer. It has a utility that takes your current image and automatically formats it to your screen. It saves the file as a .bmp. The only downside is the file is stored in the App Roaming details, and replaces both monitors photos. I'm using WallMaster for my dual monitors so it's pretty easy to sort things out.

Thanks rormeister,
I've been using FastStone Image Viewer for about a year (great tool for image conversion and making animated GIFs) and didn't know it had this functionality.

The feature 'Set Wallpaper Anywhere on Desktop' is capable of doing just what I was hoping for. It's not the most intuitive way of achieving location specific wallpaper, it looks like it's primary goal is to create framed miniature mosaic wallpapers. With enough fiddling around I was able to get what I hoped for though , great tip.