Having an eye-catching image for your class will help it stand out from others on offer, and really get the student's attention.
There are a few things that should be considered when designing your image:
We would recommend using bright and contrasting colours.
Use large, engaging text that can be read easily and at a glance when the image is displayed on a small screen such as a phone.
Consider including a photo of your face making eye contact!
You can also try using white space / negative space so it doesn't feel too cluttered, and use a sticker effect or blocks of colour under text or images to increase contrast.
There are lots of blogs and YouTube videos with tutorials and ideas about how to make eye-catching thumbnails, just search for "YouTube thumbnail ideas"
Sources of free photos for backgrounds