Casino game thumbnails need to work like profile pictures because both show up...

https://hotel-wiki.win/index.php/What_Does_the_GOV.UK_Design_System_Say_About_Color_Contrast%3F

Casino game thumbnails need to work like profile pictures because both show up small on screens. On mobile devices, a single clear focal point grabs attention quickly. Use strong contrast and simple cropping that highlights the main element