Hello, upload jpg without compression means with the less compression prossible, because there so much difference between photoshop level 1 compression and 12 level without any compression, I suppose that other software have near options. I think that Nintandbox request this because all other formats with not compression can be very heavy files, with it means for bandwidth and disk spaces for a free website.
I think that you can use png files, if it does not have very have ppi, giving a relative small files. In others case you can use Archive.org, that they do not have limit and share the links here.
Welcome to Nintandbox and I hope that you enjoy here.