I’m pretty sure it’s a limitation for new users. I’ve just increased your level from 0 to 1, so iirc you should now be able to edit your main post to add more pictures. 
Welcome to the forum btw! I always enjoy seeing National Index collections, especially when they appear so random with cards from all the different eras. Cool that you stick with just Japanese though, for some consistency.
It’s pretty outdated nowadays, but I had a National Index collection where I used cards from all eras and even all languages as well. I did decide to include all forms/shiny Pokémon, but especially the shinies made the collection a lot more expensive to complete.. It’s also the main reason why I haven’t continued it, but perhaps I might again one day.
Greetz,
Quuador