First off, would that make any sense for the time period? Would Vikings line up with a medieval fantasy? When I say medieval fantasy, I mean around the 11th to 14th century. Y'know, the medieval age, but not the renaissance.

Well Viking age equipment isn't terribly different from that of 11th century infantry with the notable exception that they lacked a significant amount of heavy cavalry, Norsemen acting as Vikings when they used horses usually did so for strategic mobility and as tools for scouting rather than having a significant number of their forces fighting from the saddle with lances and the like. You have some other chances with the way that by the end of the 11th century probably a lager proportion of people would be wearing mail and heavy gambeson and mail was beginning getting longer on the arms and bodies plus changes in shield styles from round shields to leaf shaped/kite shields. But if you put a Norseman in the 14th century people would really be noticing it given how even among specifically the infantry not to mention other arms were moving forwards in the kinds of weapons they were using and armour they wore.

Second, what kinds of armor and weaponry would they use, should I stay true to the Viking image? What did they look like?

The most common kinds of arms and armour you're going to see is a round shield and a spear along with probably something like a Saex or long knife with only a basic tunic for protection and perhaps a spectacled or Nasal helmet if they could afford one as the first kind of armour they might add. Wealthier warriors might be able to swap out the saex for or add a sword to that, we're talking a Carolingian style blade, simple guard, straight, relatively short, usually either balanced for cut and thrust work or with a slightly wider blade one that leans a little towards cutting work. Alternatively various kinds of battle axes were used, shorter handled ones could be used as a primary weapon or as a side arm to a spear where as by the end of the viking age great axes among the more professional huscarl retainers had become more common.

For the armour of wealthier warriors mail might have been sometimes used, particularly towards the later end of the period and probably more often short sleeved. Sometimes potentially they might have used Lamellar, perhaps importing the tradition from Slavs and Byzantines.

Additionally, was leather/animal hide armor even a thing? The Orcs I have now wear the hides of animals as armor, which I am beginning to question the practicality of after some research.

And while we're here, does anyone know what their casual clothing would look like? The Orcs are hunters and gatherers, but if I can, I still want them to have the Icelandic style.

While leather and animal hides might make sense for a hunter gatherer there's not much this probably wasn't was especially common as opposed to wearing woollen clothing, but obviously for that you need to domesticate sheep. But really you're going to have some problems producing a lot of Viking age things as hunter gathers. Hunter gatherers have to be mobile really at least to a certain extent to survive in groups of any significant size otherwise they deplete the local resources and their social groups tend to cap out at a certain points. As a result having a lot of the basic technology that i'd associate with being a Viking such as the ships required to go on a viking would be difficult to produce and it would be really rather difficult to set up any form of advanced enough metallurgy in a hunter gather population, farming allows a population to living in a single location permanently which isn't necessary for metallurgy but does help a lot and it allows for people to produce enough food that members of a society don't have to spend their time doing so. In a hunter gatherer society everyone has to be a hunter and/or gatherer. When you have large scale agriculture you produce enough food that not everyone has to be a farmer and so some can become blacksmiths. Without that its difficult to set up ironworking on any significant scale. The same goes for things like a professional shipwright. To organise the large Viking invasions to you'd need a larger social structure which seems likely to be difficult without pastoralism or farming to back that up with the resources to support such a structure.