Seeing as it's a degree project I don't think it really matters, sure you could reduce it to a 256 but if there are no budgets then why not?
For a cardboard box, it looks good. I mean if I had to be really picky it would be the yellowness of the texture, I'd probably tone it down a bit and make it a less saturated brown colour, similar to actual cardboard. However, I guess it all depends on what style your going for.
As someone else said, I'd look at moving on from it onto the rest of your scene. Great work!
The only other things I'd mention is that the 'hand written' text on the top right corner of the box looks like it's been mirrored and is written backwards. Though I can't tell properly from the size.