I use a weird wing shape that gives some extra coverage to my left shoulder. Think a coffin shield with an extra triangle bit on the top left side. I do a pretty passive shield style so it works well for me.
In the days of yore (1.3) I had a half heart kinda shape to my shield:
It’s just under what used to be the maximum area, 35.5” from the bottom tip to the top of the curve, back when we had such things and walked uphill both ways in the snow* to get to the circle.
With 2.0, and the removal of shield size limits, I did this, and yes, that is a long sword.
I don't like strapped shields in general for Alliance, because they're harder to get out of when you get disarmed, are packet magnets, and we don't hit hard enough to need the extra mass in a shield to help soak impacts.
Oh I've run the gambit on shield shapes and sizes, and find different shields fit different styles. I mainly fight with a curved round shield made from a steel sled, having your arm inside the center of mass instead of behind it lets you move it more naturally and fits my more active shield fighting style (works best with a max length short or min length long to be aggressive, but i also use a spear to be more defensive) though before that Ive used an angle strapped kite ( really good for a sit back and block style of fighting) and a perpendicular strapped coffin (IMO one of the better beginner shield for strapped shields as it sits the most surface area far out). That said, huge tower shields sit in a new spot of defensive style but have a lot of downsides, mainly the large walking packet magnet that you cant move out of the way, but boy is it effective against bows and melee. I'm experimenting with a new one based on the pavise shields used by crossbowman, but I wont have any feedback on that until I can play with it. I will say that there is a bit of OOG work a steel shield does if you are trying to get targeted as literally every NPC ive fought against has mentioned how satisfying hearing a *TING* when they whip a packet at it across the field. Ive put a lot of thought into shield shapes and styles and punch does work for the people who swear by it, but I just cant use them.
edit: punch shields do give you the benefit of geometry, as angles of attack are much shallower the further out you put your shield, which is the same reason perpendicular straps are more user friendly than angle straps, ill see if I can get some images to show why certain shields have the benefit they do.