The seamless integration of inspiration requires an inspiration's deconstruction into tropes, each trope being fitted into the narrative framework of your setting, given a surface gloss to match the elements that are not being innovated, and then the consideration of the combination of characterizations, motifs, narrative devices, plots, settings, and spectacle to insure that it makes sense.
In more detail, a discussion of literary elements:
Looking at the elements of the narrative from Tv Tropes, the GM is control of the following:
"Inspiration" can inform any and all of the above narrative elements. Genres are formal groupings of the above.
Noir, for example, has requirements of Characterization (gritty detectives, femme fatale dames, angry captains) Motifs (stranger in a strange land (for the back-from-the-war feel), desperation, etc..) And so on and so forth.
The term "viking" (those people from camps across the bay) informs (or inspired) each of the narrative elements differently.
For example, in a hard sci-fi genre, we can apply the idea of vikings:
- Vikings as characterization:
- A race of travelling pirates
- From a resource poor land, taking our stuff
- Our brave warriors
- They go out in ships, and fight for what's ours
- We live in small space-stations (villages) and those people on the planets won't support us
- Pale-skinned race
- Use axes instead of swords because axes are way cheaper and last way longer. (The wood breaks, you replace the wood. Very hard to break an axe-head compared with a sword.)
- Mapping the idea of axes v. swords onto space could be a "they use slow orbits instead of torching the whole way" (conserving fuel and reMass)
- It could be a "force fields instead of metal" idea
- It could be a ceramics v. metal (as seen in the Reaches books by Drake)
- Quick to anger
Here, all of these are tropes that can be applied to characterization. They are things that inform how certain NPCs behave, look, etc... The chosen tropes then echo into motifs (oh no, not energy ships again!) spectacle "The raiders flew across the sky, their shining green force-ships igniting the atmosphere behind them..." setting, etc..
You seamlessly apply inspiration into your setting (of which the actual setting is only a component) by breaking down the inspiration into useful tropes, then applying the gloss of your setting to those tropes.
Vikings is a header for a huge host of tropes. If you try to apply all of them, your setting will either have to give, or you get the cognitive dissonance (which camp celebrates) of having tropes that don't fit the setting inside the setting.
If, instead, you look at the interesting tropes of the viking, then apply them one at a time to your "setting as a whole" you can seamlessly blend inspiration.
For an excellent example of Space Vikings, I suggest Space Viking by H. Beam Piper. The central theme is barbarism v. civilization (destruction v. creation) and the rest of the book explores that idea. By deciding on a motif first, "barbarism v. civilization" and then using the theme of vikings to elaborate on that motif, Piper combines the ideas.
There are many instances of low-tech and resource poor raiding foreigners in sci-fi, and all of those are inspired by various forms of the viking idea. By considering the different tropes involved, they can be mapped back to real-world tropes. If the raiders sell to merchants, then they're pirates. If they keep what they take, they are vikings (very broad generalization, there.) Applying a "gloss" means fitting setting-appropriate elements to the innovative trope introduced, such that the presence of the trope reinforces the setting, rather than distracts.
The Soetti from Retief! are an excellent example of the viking tropes being heavily glossed. The desperate need for resources is there as is the danegeld trope, but they exist within the setting quite neatly. It is only after thorough reflection that the Soetti can be given the "Viking" label, rather then casting them as blond-haired berserkers in a proud warrior tradition.
In both books, we have vikings. In Space Viking, they inform the whole setting. In Retief! they inform some of the antagonists, quite seamlessly. By comparing and constrasting the two books (and getting awfully decent reads out of both of them) I suspect the differences and similarities will offer inspirations to you that don't need to be re-glossed to fit into your sci-fi setting.