Question: I need a tool which allows me to upload an image with a device(like [this](http://images.anandtech.com/doci/9686/DSC_3927_678x452.jpg)) and then to upload my app screenshot on the screen. What can I use? I don't need a tool like placeit, I need to upload my own image and my own screenshot. And also I don't want to use Adobe Photoshop. 

Placeit.net allows me to put my screenshot in many preset device images; however, i want to use my very own device image and on top of that to add an app screenshot. I can't do it in PS because it's quite time consuming (my images are rotated, skewed, in perspective etc.) and I need to do multiple images so I'm looking for something a bit more automated.

Answer: 
I am very sorry to say but the best way of doing this is actually by using Photoshop.

But the process is so simple that (with a little more dedication) you can use even Paint to do something like you described. You just need to find an image with a phone, it doesn't matter if it already has a screen. You will add your own image over the screen with a little bit of resizing and crop. 

Depending on how realistic you want it to be you will need to add reflections and shadows to it.

> 
> An advantage in using Photoshop is that you will find a lot of free
>  mock-ups out there that will simplify your work.
> 
> 
>
If you check out some more advanced mockup templates for Photoshop you will learn that you can do all rotation, skewing etc. in layers or actions, which - after an initial setup - will allow a very quick replacement of your screenshot without much manual work.

Another option might be <https://www.getscenery.com/> where you could add your own backgrounds but you will need to use the hand/device photo of the software.