I started with stacks of art magazines. When they became overwhelming, I started cutting out the images that I liked. I would stuff them into a shoe box and thumb through them when I needed some inspiration. Eventually that shoe box gave way to a notebook. I placed the photos into plastic sleeves. Over time my tastes have changed and I've learned more about art. So some images have been thrown away and new ones have replaced them.
But, I also do a little more with them now. I label the images with terms that I think apply to the painting. I might use "atmosphere" to define an image. Another might be an "abstract composition" or "color". Texture or brushwork could be labels to use. And some paintings have more than one label.
I found that by labeling the photos it would make me stop and think about the painting. What is it that I like about it, what is important, what inspires me in my painting. Every time you have to stop and think, define and ask why, you will learn a little more.
I had a student ask me recently if I thought it was OK for her to copy another artists photo. For learning purposes I think it is OK and helpful. But, you shouldn't be selling the work if it is a direct copy. Although, you could try a different direction. You might like a color scheme that an artist uses. Make your own composition and use the color scheme. It could help you learn how and why it works.
If you like one artist's brushwork analyze it, why, what do they do differently. Try to apply it to you own work. So, the next time you need some inspiration, pull out a scrapbook!