A quick question to the Photoshop Wizards among you...
I have a banner template like this:

What I would like to do now is create a Photoshop batch that lets me select a number of images which get inserted instead of the placeholder layer on the left and creates one banner for each variation.
Is that possible? How?
Record an action for it. I'm not sure if you can make it parse through a folder for file placing but you could definitely do it so it opens each image then edits it to make the banner. E.g. folder full of all the banner images and a stock text image somewhere (or better yet just make text in the action itself). Action would be: Open image. Change image size to 250 high, keep aspect ratio. Expand canvas to 400px from left side out. New layer, white, put over the right hand side. Make text. Export for web. Alternatively if you have a template that gets the images inserted into it but I've never tried that. E.g. open X image (template with text only), place file in document, move to top left corner, resize to 250 px height with aspect ratio maintained, rasterise layer, crop it to 150x250, export for the web.
Just play with the actions until you get what you want. Make sure to do so in some random new folder with copies so you don't accidentally save over all your files.
I find it easiest to set my banner size first as my canvas size. I typically go double res while I work then scale it down for export.
I'll then build out an overlay.

I will keep all of the overlay elements in a group. Then make another group and drop all of my images in there. I then position all images so they look good within the overlay. One of the benefits of the overlay group is that you can make different variations then show/hide them for different versions.
Once you get to this point it is much easier to record an action like zeno suggests. Could be as simple as hiding the top layer in the image group and saving for web then repeating.
Keep in mind, I'm pretty sure you need to have layers and groups named as they were when you recorded your action.
Another option which may or may not save you time is to create comps for each variation then export layers as files. Unfortunately if you were to just export layers it just spits out a file for every element in your psd.
Actions are one way to do it. I think that you have to use file>automate>batch to run a whole folder of images
I do things differently. I use image>variables>define. Then pick the layer you want to switch (eg your image layer). You will need one layer called "ID". Should be a text layer that you toggle off (not visible).
You then need an excel (CSV) file like this
ID IMAGE
1 fullpath/image1.jpg
2 fullpath/image2.jpg
The headline should be the same as the name of your variables and is CASE sensitive.
Then import your CSV through image>variables>dataset.
You should be able to browse the results at that point.
Then File>export>data set as file
Save all your files as psd (no choice I think)
Then File>go to Bridge
Find your psd files. Select them.
Then tools>photoshop>image processor =>use that to batch save your files as jpeg
I might have missed some details because it's been a couple months since I've done it. I thought I would make big money by having state specific banners on POF but that didn't work for me obviously.