Yes it's OK to put Ketchup on eggs.
If you like putting Ketchup on your eggs then there's nothing wrong with that.
Ketchup goes very well with eggs and I cannot eat eggs without Ketchup myself or at least something to flavor it.
I like to also eat Tabasco Sauce and sometimes Jalapeno Peppers with my eggs as well which add flavor to the eggs.
Some other things you can put on eggs besides Ketchup are Hot Sauce, Tabasco Sauce, Mustard, Salsa, Taco Sauce, Nacho Cheese, Melted Cheeses and even some pepper.
Adding some Jalapeno Peppers to the eggs is also good.
I like to eat Jalapeno Peppers with my scrambled eggs and also top the eggs with Ketchup which makes them even more delicious.
The Ketchup adds flavor to the eggs and makes them easier to eat as I find eggs without Ketchup disgusting but when adding Ketchup to the eggs I can eat them with no problem.
I also like to put some hot sauce on my eggs sometimes as well and the hot sauce makes the eggs taste better as well.