The Baltic Region in the Middle Ages
If there wasn't a Baltic setion on this website, then the domain name simply wouldn't make any sense. However, as I have been researching medieval history more and more, my interests have diversified, and I'm not as single-minded about Baltic clothing as I once was.
So, what is the Baltic region?
I prefer Baltic 'region' to 'states', because it is a more ambiguous term, that doesn't just mean the modern-day countries of Latvia, Lithuania and Estonia, to the exclusion of all others. Iron age and medieval Baltic tribes weren't considerate enough to look into the future and know where the modern borders of countries would lie, so just looking at archaeological finds within the modern Baltic states would exclude fascinating tribes like the Old Prussians.
By including countries with coastlines facing the Baltic sea, we can include the Russian enclave of Kaliningrad (Königsberg), Poland, and Finland.
But Finland isn't Baltic!
Well, strictly speaking Estonia isn't either. The early inhabitants around the northern Baltic sea were Finns, whose decendants include not only the Finnish, but Livonians, Estonians, Karelians, Ingrians, Veps, Votes and other modern groups. Looking at finds of jewellery worn by Finnish people can give insight into similar fashions worn by the Estonians, for example.
But you forgot Belarus and Ukraine!
My personal focus is generally Viking-age, before the Grand Duchy of Lithuania, or the Polish-Lithuanian commonwealth existed, so places that by the later middle ages may have been considered Lithuanian won't be discussed here.
May I suggest visiting the Polish-Lithuanian commonwealth site?