I am creating a character who spent the first 19 years of their life in Estalia and I know very little about their people and culture. I know that they hate their neighbors to the east and that they fought of an invasion from Araby, loosely based off from Spain and Italy, but that's about it. Do they have much of an interaction with chaos? Undead? How likely is it that a human citizen has had dealings with any of the other races?

You know most of what is out there.

I did find some player made content, maybe it help.

Estalia Player Made

Mad Alfred's site has some stuff on it if you hunt around, including a gazeteer. There are maps on glitzman's site.

Not much Chaos. They dislike high elves because Ulthuan blocks their efforts to explore the New World.

Earlier editions of WFBattles note, "The threat of Chaos seems very remote here." and that the Estalian Kingdoms are not united, have a strong tradition of seafaring and Magritta (Kingdom of Astarios) is the strongest naval presence in the southern old world with strong trade now to Araby.

They do, of course, have Skaven.

This comes from Mad Alfred's gazeteer has a snapshot description of Estalia. Its a couple of editions back in WFRP terms but I don't think that matters in this case.

ESTALIA

Since the Arabians withdrew from their conquest of the land, the kingdoms of Estalia have grown in strength and influence. The most powerful and riches of these kingdoms is Astarios. Its lone stance against the power of Araby and its hold on its capital of Magritta has given Astarios prestige among the Estalian people. It was this prestige that allowed Astarios and her allies to extend their influence (through marriages and political alliances) throughout southern Tilea during the middle of the 23rd century until its coffers were depleted in the beginning of the 25th century. Part of the economic drain could be attributed to the overt attempt by Astarios to reign in the pirates of Sartosa, as well as their attempt to subdue Tobaro.

The second most powerful kingdom is Tigarre with its capital of Bilbali. Like Astarios, Tigarre led her allies into expanding their sphere of influence beyond the Estalian frontier. The invasion of the Duchy of Brionne was short-lived, however, and lasted just 12 years.

With the exceptions of the Obregon and Cantonia, the other coastal kingdoms and duchies tend to ally themselves with either one of the two most powerful kingdoms. Astarios can nominally count on the support of the kingdoms of Avila and Santoyo, as well as the duchies of Zaragoz and Gualcazar. In contrast, the kingdom of Navareno and the duchies of Alquezaro and Barboza follow Tigarre's lead. Obregon (with the duchy of San Luis) and Cantonia tend to follow their own respective policies and only join one or the other alliance when it suits their purposes. The small duchies and counties of the Irrana Mountains are fiercely independent of any of the coastal powers and serve as a strong barrier between Astarios and Tigarre.

As a peninsula, the sailors of the coastal Estalian Kingdoms are among the best seamen in the Old World. If not for the Norse, the Estalians would have been the first to land in Lustria (despite Tilean claims to the contrary). With strong trading relations with Araby, the kingdoms of Astarios and Tigarre (with Obregon and Cantonia playing minor roles) have turned their attention to expanding trade and contacts with the land across the Great Western Ocean, as well as the Southlands, Ind, and Cathay. Conflict and competition with the Norse, Tileans, and High Elves of Ulthuan are seen as necessary evils to which the Estalians are willing and able to respond.

Find the fan-produced Estalia warhammer fantasy battles book. Also, there are details in the Bretonnia 2e book. http://battlereporter.blogspot.com/2010/09/estalia-new-wfb-army-book-pdf.html

No idea how i broke the link but fixed it. Kept making me edit it when i clicked it. Wierd

Yeah, Emirikol , that was the same site I was trying to link. But the thing failed to work. I remembered someone linking it before on the forums, plus the other areas.

loosely based off from Spain and Italy, but that's about it.

I think you can add Portugal to the list of historical influences, as well.