This is a great start! You've already given me some food for thought - the '1 day travel' scale is inspired! I've always worried about scale on my maps; I spend ages trying to work out how far things should be away from one another and agonize about how to depict the scale. I never even considered specifying distance as travel time
If I could offer some creative criticism, though - assuming that your travel time is given for a person travelling on foot, you've got a heck of a lot of cities in close proximity to one another; from a rough measure you've got (in the centre) 5 cities less than 6 hours away from one another. I'm definitely not an expert on cities but you should consider that cities are quite few and far between - they certainly don't pop up right next to one another - there wouldn't be enough room for them all, for a start, and cities require an alarming amount of produce to survive which means that a lot of land around the city would be given over to farmland (there might be a village or town in the midst of the farms - typically along frequently used trade routes - which would be almost like your suburbs). City placement is also important - ports mean cities because people have to go through them and they generate trade; places where two or more trade routes converge can, sometimes, mean a city (though, more often than not, it will be a village or town which has an inn or two to support those travelers who wish to stay the night); strategic locations can mean cities, too, where a castle has been built to protect the surrounding countryside (or as a display of some local lord's power and deep pockets) and a town has grown up around it.
You've got the coastal towns idea down, but watch out for those towns which appear to be in the middle of nowhere - why are they there? If you can answer this question in a way which is plausible, leave them in. If not, they shouldn't be there. Is it a mining town huddled against a mountain or is it a fishing village at the edge of a great lake? Is it surrounded by farms which provide sustenance for a nearby city? Is it next to a forest and provides lumber? Always question what's going on in each of your towns.
I'm going to leave it at that - hope that helps you!
Great first effort on a map, I really hope to see some more soon!