anyone know how i could do this? it might need more than html

let's say there's a thread on a forum where people post pictures
(not so important other than the act of collecting pics)

i want to put them all into a table (a square essentially, it doesnt have to be an actual table)

when i put the first pic in, i want it to be the size of the full table

when 3 pictures are entered, they would each be 1/4 the size of the box with one white/empty box

when i put the forth one in, i want it to be 1/4 the size of the total square and so on

ie. i could start with a 10x10px picture in a 1000x1000 table, and the pic would be stretched to that dimension

once there are four, each pic would be 500x500 and so on

in the end there would be a ton of images (10,000)
each of them being their natural size

how can i do this?