You can actually use the word "egal", without sounding rude, if you wrap it in a sentence. Generally speaking most words would sound rude, if the are on their own. However, if you are looking for a nice way to phrase that you would be okay, with whatever that person chooses, I would recommend either something like "Das sieht alles gut aus, Sie können gerne einfach eins aussuchen." Or something like "Einfach irgendeins." would be more common. Your suggestion with "Irgendetwas ist okay." Would be understandable, but not as smooth.

You can actually use the word "egal", without sounding rude, if you wrap it in a sentence. Generally speaking, most words would sound rude, if they are on their own. However, if you are looking for a nice way to phrase that you would be okay, with whatever that person chooses, I would recommend either something like "Das sieht alles gut aus, Sie können gerne einfach eins aussuchen." Or something like "Einfach irgendeins." would be more common. Your suggestion with "Irgendetwas ist okay" would be understandable, but not as smooth.