Always great to see your stuff!Nothing too complicated really - black cloth on the floor and then stand at the foot of the jersey and shoot downward. My shoes and excess black material are cropped out of the photos to give them a more uniform appearance. I've also learned over the years there is no substitute for a lot of good natural light, especially when trying to shoot the black jerseys. I know I could use a different color background with the dark jerseys (I tried gold at one point) but I like that with my web site being a black background formatting, it helps the background of the photos "disappear". All the big gold rectangles on the website looked goofy in my opinion so I scrapped the idea and stuck with all black, all the time. Unfortunately the black jerseys sometimes they disappear in the background as well and you just see striping and numbers.
I think the collectors that have a more angled image are likely not cropping their photos, so they just stand farther back and shoot at a shallow angle to eliminate anything they don't want from being in the image. When I first started I would get up on a chair so I could lean out almost over the center of the jersey, but since then I've discovered I don't have the free time any more to add the additional step to the process so I just stand on the floor.