so for me as a dom when I was more heavily into online play I wanted to know things like their timezone, likes, dislikes etc. I wanted to know what they were expecting out of the relationship, you would be surprised how many times a girl would say she wanted to be a sub do one play station and pretty much vanish with no word. How often you are expected to communicate. Some like just a task some like to chit chit all day. I wouldn't say pictures are a red flag, for me I wanted some kind of verification it was a girl if online play. I would work with them let them do a clothed picture doing something silly, occasionally a voice recording or something. Rarely would I let it go with no proof.
I almost forgot one of the overlooked ones, figure out if they are looking for lots of girls or just you or if they have any currently. Ask them their experience that they have, or tell them the experience you have. Give them a scenario and ask them what a task would involve with that, some can go 0-60 real quick some will start you out slow. Most of all after talking for awhile you will figure a lot of it out if they are right for you. Since you are a girl you can stay picky because you are going to have so many guys throwing themselves at you that you can afford to be picky. I hope that helps and if you have questions feel free to pm me if you like and welcome to kink talk.