Nice first map - or first published one :-). I'd give you a smidgen of rep just for being bold enough to jump in with a contribution, but the maps' worth it anyway.
I have to stare at it to think of what I might suggest to change. The suggestions about the wave lines and coastline were good, and they do look better. There's places where I might omit the wave lines - like the bay by Iuth is okay, the one by Andoroun is iffy, and the inland bodies of water like near Zheo or Khasea I'd skip the concentric wave lines. If you like it, ignore this - it isn't *wrong* per se, nor does it look *bad*. The gradient onshore and offshore works, for the reasons suggested. If you want a flatter look, the onshore and offshore colors could've been left as-was and a find-edges rim of a single pixel (onshore) would improve the land/sea contrast. Might even only need partial opacity, just to sharpen the edge.
Again with respect to contrast, you're letting the image you're using to add texture almost overwhelm your own map in places. Almost makes me want to turn the page over and see if there's another map there, bleeding through :-). A completely random grunge effect might be as effective, without distracting. Your overall look is subtle, pastel - it would be enough to have a bit of dark border, to keep the eye from running off the edge if you will. If you like the 'gold frame' thing you almost have going on, maybe a more abstract pattern would suffice? Again - improvement *maybes*.
With the geography - most is spot-on. A delta is more what a river does after it hits a coastline (water shows, dumps sediment, and grows land outward) than what it does before it reaches a coast. A bit of the latter is true - if the terrain is superflat, you'll get meanderings and alternate channels and such - but your almost straight end-of-delta constrains the look to be all onshore. I can imagine conditions that would scour the seaward bits away - like strong crosswise currents. But your inland sea would be not super likely to have strong currents.
Your Aletheal range is nice enough, and a pretty typical representation of "over here lie forests, and over there are mountains, and never the twain shall meet". It would 'anchor' the range more if you interwove the two - forests DO typically run up into the mountain slopes quite a ways. Now, I understand you're relying on some nice canned mountain symbols -- but you could maybe stick some peaks, or their shoulder ridges out toward the plains, then run the green a bit up in the valleys. It's understandable to have to have some separation - totally cover the mountains with clumps 1/4 to 1/3 their size, and you'd lose the relief. <shrug> tradeoffs are okay :-).
The river network is nice. Where that imagination of yours :-) is seeing flat river valleys, the lower reaches could do with some looping wiggles. You HAVE to exaggerate the width of rivers at this scale, else they would disappear sub-pixel width. So they're okay as far as that goes - wiggles need not be exact; generalized representation would do.
Oasis of Sur, Port of Olin labels could be tweaked away from the roads. Aletheal Mountains and Lorn Forest labels could benefit from being spaced out to better 'claim' the extent of their areas. Culture/ society-wise, I'd expect some more cities or towns right on rivers - being early conduits for travel, trade, agriculture, even (if your era matches) power. Ditto coasts - I'd figure more ports - though some of your near-coast cities might just be ports symbolized away from the edge of the water?
Anyway - suggestions all; it's pretty good already. Amen! about the addictive nature, and getting pulled into the world creation. I find maps telling stories all by themselves :-).