That is a very broad question, some definition might be in order.
Is the focus on visual appeal or maximum safe storage?
A combination of both. I have safe's for the really rare stuff. This is for easily replaced items that I want to display. I want to display as many as possible given the area I have to work with.
Do you have favorites or particularly special firearms that you want to single out from the rest?
I have not thought about that. But, there are a couple that I would probably want to highlight.
Are you the type of person who gets something set up right and leaves it for years or do you want to be able to change things around?
Once done, I'll probably leave it a long, long time.
Is your collection fairly fixed? Do things come and go? Constantly expanding? Being honed down to the best examples only?
My collection is expanding as money allows, but I don't typically sell anything. So, fairly fixed. I could rotate items in and out of safe if I wanted to once the display has exceeded capacity.
Is your collection static or active? Ie will the rifles stay in situ unless being cleaned or are you constantly taking them down to handle, examine, shoot, photograph or show to friends etc?
This room is just for me. No one other than immediate family will be allowed in and it's in a very secure location. Most of the collection is static. Guns I shoot will be located in easily accessible areas either on the display or elsewhere in the room.
Approx how many rifles, muskets, carbines and pistols do you want to display/house?
As many as will fit in the given space. The space will hold more than I currently have. I want to allow for expansion.
How do you group them? (Basically do you want to be able arrange them with muskets next to cavalry carbines or all the muskets together, then all the short rifles, then carbines etc?
Good question, I need to get them out and start grouping them. AR's and AK's are shorter than M1's and K98's, which are shorter than muskets. Probably will group by partially by sized and then by year or type of rifle. The muskets are long and I thought they would look nice displayed horizontally. The modern shorter stuff probably vertical. The older milsurp stuff probably a combination based on what room I have. In other words, some of the nicer ones, I might display horizontal with bayonet and maybe bandoleer. Rougher versions vertical.
Do you want the vertical rifles action out, trigger guard out or side on? (Or angled so you can see the action and some of the side?) Vertical or leaning?
Wow, another great question. Initially, I was thinking trigger guard out. But, maybe angled would look better and/or side on. Although those would take up more space, right?
Do you want the rack itself to be a feature or to disappear?
Probably disappear. Simple design that showcased the gun.
Do you have a style preference or a style you need to match?
No
Will it have lighting on, at or over the racks?
There are can lights that will highlight the racks.
Do you want/need storage space included for books, kit, memorabilia or ammunition/accessories?
Yes, probably some. Looking at the dimensions, I'll probably have some room left over so I was thinking I could alter things to allow for a shelf to store or display memorabilia. One of the things I need to do is look at all the memorabilia, and determine what to display.
Do you want bayonets stored with or on them?
Another good question. I was thinking in the case of the muskets, probably beside them. The others, probably a combination with the horizontal ones have them and the vertical ones not.
Do you have either legal or self imposed safe storage criteria?