[quote=@Zombiedude101]
I'm gonna be honest, I may have changed my mind; I'm struggling to write a background for the characters I have in House Royce and part of me things I might have an easier time going for House Blackwood. Less established characters in that sense.
[/quote]

Pardon? I am not sure what you mean exactly. There is quite a lot of established canon on the Blackwoods during the Dance. This is taken from the wiki:

[quote]Lord Blackwood supported the claim of Laenor Velaryon in the Great Council of 101, but the council ultimately chose Viserys Targaryen as the heir of Jaehaerys I Targaryen. A Blackwood fought a duel with a Bracken over Rhaenyra Targaryen in 112 AC, but the princess eventually wed Ser Laenor. The Blackwoods supported the blacks of Rhaenyra during the Dance of the Dragons. Lord Benjicot Blackwood and Red Robb Rivers, the Bowman of Raventree, participated in the Battle by the Lakeshore. Lord Ben had one of his best archers, Billy Burley, mercy kill the dragon Tessarion after the Second Battle of Tumbleton. After the civil war ended, "Black Aly" Blackwood, Bloody Ben's aunt, married Lord Cregan Stark in return for allowing King Aegon II Targaryen's pardon of Lord Corlys Velaryon to stand.[/quote]

Obviously that last part can't happen now, since we're having a customised House Stark.

As opposed to what I found for House Royce:

[quote]In time, House Royce regained much of their pride, wealth and power, for during the rule of Lady Jeyne Arryn, Yorbert Royce, was the Lord Protector of the Vale, going to the Great Council of 101, because Lady Jeyne was a minor at that time. The Lady of Runestone, several years later, was Rhea Royce, who was married to Daemon Targaryen, a big player in Dance of the Dragons. During the Storming of the Dragonpit, Ser Willum Royce was killed and the Royces Valyrian steel sword Lamentation was lost.[/quote]

What it comes down to is that there is lore for both houses. Now, the way you flesh out characters and histories is up to you. I think you have leeway (hehe, LEE!). I personally think that you're better off working [i]with[/i] canon instead of disregarding it entirely. That is my preference. Alternatively you can take on a different house altogether, with less or no historical entry. Ultimately, the choice is yours :).