Thank you for getting back to me! Pixabay and Unsplash both state on their websites that the images on there may be used without credit. However, if it makes the currators more comfortable then I am happy to start mentioning the use of their sites in future posts.

The thumbnail image was one of the default templates on Canva, I kept the default image and background including the arrow and I changed the lettering. If you look through the templates yourself you can see it, but I am also attaching a screenshot of what it looks like to me - I did not take the image from somewhere else and/or steal it.