I guess it depends on what direction you want to take magic?
Magic is Common: Everyone can cast some weak spells, lots of magic items, but still a medival style world (the "ancient empires" motif) You can open up some new feats (the spell feats from Comp Arcane, Spelltouched Feats from UA), and have everbright laturns and self-carving knives. Low power magic is common, if not trivial.
Magic is Accepted: Similar to the above: magic is still hard to use (requiring training and suffcient ability scores) but spellcasters have no special stigma. Magic is no more common, but its acceptance allows for its intergration into society. This is the Eberron approach.
Magic is technology: This is pure fantastical. Crystal Ball Phones, Flying-Carpet Cars, Mecha-golems, etc. Almost all magic is used to replace or augment technology, or it can exist with(or compete with) real technology. This is more Final Fantasy approach.
Magic is Power: Magic is rare, but powerful. High level spellcasters abound, and epic spells are known of if not used. Most of the common folk know of this kind of magic, and steer clear of its near god-like power. Low level magic is moderately rare, but high level is much more common (but still unique, there is no +2 swords, but there is Stormbringer). This is the Forgotten Realms Approach.
Magic is All: Magic is SO infused that even commoners know spells and simple incanations. There is no non-spellcasting classes, even knights are rogues have magic to fall back on. It encompasses much of all the above, and is occasionally used in some Anime (Bastard! comes to mind).
Once you know where you want to enhance magic, you can begin to look at how that would change things. I'm sorry I can't reccomend a setting with the work already done for you, but I tried to cite examples whenever possible.
Good luck.