With the Kobo Start Menu you can make your own HTML page, including an image if you want.
Here is one that I made, the posts around it should be enough to make your own. This is a Poweroff screen, I have my sleep in Koreader setup so it is just the page I am on frozen, so I can clean the screen or pocket it. A quick flick of the power slider and everything is as it was when put it to sleep.
https://www.mobileread.com/forums/att...2&d=1404508592
There is also the demo mode, in the stock Kobo software. You could also make
a .cbz file, to read, then sleep on the page you want.
Luck;
Ken