There is a way, besides of Veyon which could meet easily your need, and give you ideas : BGinfo.
This is a small exe launched automaticaly at each start up of a computer and stopped immédiately after :
function : create a desktop wallpaper with the information you may need, color wished etc...
Then you can have: user name, host, group, IP, MAC...
you can chose position and size of all this.
for me top right, about 1cm height characters (i can see them in real from my desk and from veyon also)