Welcome to the guild - i'm glad you delurked! First off, jumping right in with a map in your first post is worth a smidgen of rep, all by itself. Then the map has promise. The land outline is pleasing, and you've got some nice little wave lines rimming it. The feature placement is a little haphazard, but not totally implausible. What may be subconsciously griping you is that you have three fights and some madness going on.

First, the colors and textures are a mix of sorta-photorealistic and brightly symbolic. Neither's bad, but the mix is puzzling; the texture and tatters of the paper say it's handmade and hard-used, yet the pigments are as bright as a mapper could first put down. Then your labeling is in tension: crisply typeset uberlegible city names vs. an artsy tough-to-discern display font for the states. Then (again with the paradoxes) the labels have two different digital effects applied: pretty, but not belonging on tattered old paper. When you pick an effect or a symbol or a texture, if you're shooting for an impression of in- character cartographer-was-here, think about how he would have produced the effect... and would he have. Then the third related clash is that the textures imply orbital photo data, next to sketchy linework, next to bold inked-perfect lines... Which vastly different method did this oldnew ancientmodern highlowtech dude use? Samplers and patchwork are nice for embroidery, not so much for maps. And it isn't that any of those characteristics are irredeemably badly executed, they just struggle against one another.

Lastly is the madness. Water on your world does some reeeeeally weird stuff. Take a thorough ramble through Redrobes' most excellent tutorial on Getting Your Rivers In The Right Place - it is stickied near the top of the Tutorial/ How-to forum. Maybe your subconscious is taking you to task for conduct unbecoming to a watercourse :-). I'm not against the bare-parchment as water look; it can be really effective, particularly if you want to deemphasize the sea. But your mapper obviously had access to blue pigment; witness all the painstaking hand-applied (?!) washes around the city labels. Were I him, I'd have put at least a bit of blue offshore to set off the land. In fact I kind of did, once ... see my Marglyn in my Aurora-1 gallery.

All that and not a word about brushes -- sorry, I know nooothiiiing of brushes' use! Other folks can better advise you there. Really - I do like a lot of the aspects - maybe you just have two or three different styles of map all mixed together.