I just found a new tool – absolutely free, for creating 3D images of your book covers. Love it, love it, love it. So easy to use, unlimited use and great PNG transparent images for using on ads. Want to try it out? Here it is 🙂 https://diybookcovers.com/3Dmockups
The other tool I use, to upload my pics and create ads, is Canva. Also free to use, although they have reduced the amount of stuff you can do for free it is still an amazing free tool. https://www.canva.com
This little ad just took me five minutes to create using the above two links. Why not give it a go?