You're right, the colours are nice on this map.
A few suggestions and opinions from me (I'm going to assume, since you mention this is practice, that these are suggestions for your future mapping adventures):
--I like the texture/colour of the seas: perhaps next time you could show a change in water where it approaches coastlines, and on rivers.
--the mountains currently seem to be stuck on top. I think part of the problem is the starkness of their black, and the other aspect is that the land 'beneath' them is the same green as elsewhere.
--additionally, I don't know if that style of mountains suits this kind of map. Mountains depicted as icons on an otherwise topographical-looking map seems disjointed. A better approach, in my opinion, would be if the mountains were shown as if from a satellite view.
--the marbled pattern of greens on the land looks good, but possibly also problematic. At the moment it looks like a painting (which is fine) but from a practical sense, what do the changes in tone mean: does it indicate more/less vegetation, higher/lower altitude? Maps are, fundamentally, about conveying information, and I think the marbled effect looks too random. What if you wanted to add farmland? different types of forest? hills? etc.
--this point actually kinda brings points 2 and 4 together: it is a bit too green. And its green-ness gets in the way of other types of terrain. I'm not sure how easy it would be to start adding deserts, steppes, scrub, or the mountains/farmland previously mentioned.
--there is a tendency towards darkness (especially around Goodley) which can obscure details, if you wanted to include them.
--I'm assuming, as a practice map, you weren't too worried about coastlines/rivers. Just in case, though, I think the rivers should taper as they move away from the coast, and the coastline should be more diverse and rough (the islands in the middle and SE especially look too regular in size, shape, and placement).
--some labels are a bit off: Byne Bay, Withal Bay, Derna Bay. It is probably just that the text is in too large a font. Smaller fonts will let you place the labels better within the feature, and not overlap the land. But then, I'm pretty rubbish at labels, so I can't be too judgemental.
--one last point, and this is a trivial one (and might just be my opinion): do the runes around the edge of the map suit the style/theme of this map? Runes to me suggest Norsemen, and hence wintery terrain; not green and lush, as this appears.
After all those negatives (hope it wasn't too harsh), let me repeat that this is a very nice map.
I also like the Max-esque symbol in the lower left. I've been thinking about trying that out, myself.
THW