One of the weakest parts of DQ was the the skill trees, no context was given on any of the skills unless you moused over them.
This is just a mockup, but would commissioning visual skill icons representing each skill on the skill tree cost a lot? They could still maintain their round/square shapes, and have a blue/red border around them, but they would look much nicer as icons.
I think they’d be too small.
But if you want to go through with this, I recommend only using 1 color (white).
Oh! I really like the idea of doing skill icons in black and white to make them extremely easy to see. Black Out The Sun could just be a black circle with 10 white arrows over it, Armor Break a black shield with white cracks in it, Devour just a row of white fangs going up and down. A very minimalistic, low cost style. I bet Lars could do most of those himself, or ask the community for help with them easily. 
I think these could be reworked, too, though instead of black and white I think it’d be better to have red and white and blue and white, to keep the information about the nature of the skill (offensive/defensive), like it is now.
When I saw “white only” I mean white icon with transparent background (so you can see the red/blue circle/square behind the icon). :V
Those of you who follow me on twitter have probably already seen it, but I’ve been working on this 
I’m going with Alice’s idea (Red+White / Blue+White), so you keep the shape and color information of the skill gem, but just add an icon.
EDIT: as for cost, I found this set of free icons that are royalty free to use, so it only took about a day’s worth of my time all in all, and no money out of pocket:
http://game-icons.net/
That’s exactly how I meant too! 
Now that I’ve seen them in-game, can the buttons be shrinked? They look soooo big.