Not really sure how well mixing text labels and number labels would work, but in the end, the only way to know is to try and see if you are happy with the result. There are no absolute rules you have to stick to.

If I were to do that though, based on the elements in your list above, I would probably use text labels for geographical features and town names, and then use numbers for "interesting locations" like battle sites, ruins, cultural location, etc.... This seperates "proper" map information from supplementary information.

That's generally a good approach. The most important for people reading your story is to identify the places they read about on the map. Then you can expand on it later with more names if you write more stories set in that location.

A good style can never have too many symbols.

• Symbol varity is always good. Just variants of some of the same symbols would be great, like variant bridges and castles and towers and more
• Different races and cultures, as you mention elves, dwarves, halflings, orcs, but also culture-inspired like middle-eastern, far eastern, jungle tribes, aztec/maya inspired, bad/evil lands
• How about a mountain symbol with a dragon on top of it, and a volcano and a mountain with a mysterious cave
• Ships and sea monsters
• Windmills
• fruit trees
• a black cat pushing things off the edge of the map
• icebergs
• all kinds of ruins, cities, castles, towers, etc
• a snow and ice fill.

By default, templates only contain references to the fills used for the style (You REALLY don't want to have them all listed, trust me :)), so that means that drawing tools not made for the current map style will show up using the currently selected fill (see your status bar), instead of the actual fill used by that tool in it's native environment. (Your current map seems to be the Ancient Tombs style)

There's more information in this FAQ topic, including how to import the fills to the current template:

Not for lines. Polygons gets a hollow middle whenever the line width is greater than 0, but lines will be solid all the way, unless you use the "hollow" fill style (You're not, since your rivers are using a bitmap fill) OR you have an Edge, fade inner effect on the rivers, where the inner opacity is set to be lower than the outer one.

Looking at your drawing, you do have an edge fade inner which is way wider than your rivers which is also the partial cause of your rivers being very difficult to see. I didn't notice that immediately when I looked at the map earlier because I worked with effects off to see it without the glow. You can try changing the width of this effect to something like 0.2 and see if that works for you.