Here are my observations/suggestions:

The contrast is all over the place, particularly some of the labels that are barely noticeable.

Try to think of how the map was made and let that guide how you present things. Was it drawn with pen and ink, painted with watercolours, stamped with woodcut blocks? Think about the physical properties of those media and try to replicate them where they are used. If there's something on the map that is just 'there' without any any particular medium behind it, it will make the map look artificial. The nealines are a clear example of this, but so is the overly clean boundaries of the background colours which look like they were meant to look painted. It would look more convincing if it didn't line up with the drawn elements quite so perfectly. For instance, along the coast, the blue could cross over onto the land slightly in places (can conversely the brown could cross over into to the sea.

The neatline and scale really don't fit. Besides the way they look rather obviously not drawn, they just don't mesh stylistically with the rest of the map. They are far too modern.

The mountains/hills are problematic. The look like they were scaled at different factors from each other which makes them look different from each other in an artificial sort of way. There are also some odd white artifacts on some of them.

Your label placement could do with some work. You should try to avoid placing labels across other features like rivers, roads, and coastlines. If it's completely unavoidable, try to adjust the glyph placement/kerning so that the label has a gap to "let the symbol through" without touching. You might also want to try putting labels for linear and area features on paths.

There's some pixelation on some of your rivers and coastline. It looks as if you upsampled the map before adding the other features. It'd be a good idea to smooth these out.