Yes, you can just grab one grayscale photo and make it into a monotone.
But My approach would be taking advantage of your palette.
I wrote a previous post using only black and a color: Preparing design for duotone printing?
And here is an update using colors other than black.
These two cases were made using the same technique I explain in that post, separating the channels and adjusting the curves. I used Red channel and Blue because my main objective was to have a "skin tone", not an exact match, but at the same time having some colors to play arround.
First of all, choose a style you want to achieve. And choose a dark color. The first objective of this color is to print the main text at 100%.
Then you have different options, choosing a similar color, a more happy and saturated one, so your images have more life.
Or you can use for example a "complementary" color, this way you can mix them and have a darker and more neutral one.
Do not choose two light colors. If you need a light one for something specific, like a logo, see if you can choose a darker one and use it at 50%.
I was exploring some method to simulate a lighter Pantone using a darker one. Here is one. This will not always work because as these colors changes, also the saturation (and hue) changes.
Choose your light color and measure it with an HSB or HSL color model (I am using Corel Draw here)
If you can, push the saturation all the way up, this is at 100%
Now measure that new color as a Spot color (Pantone)
Now you can use this at a lower percentage.
It is not perfect but it surely helps.
Now you have an additional color to play around!
(Original images by pexels.com)