The more LJ minimizes it, the less quality you get in the picture. If you click on the picture, you get the album it's in, and if you click it again, you can see it full-sized. In order to not make it look smaller and awfuller at the size that will fit in your LJ easily, you have to shrink and crop it on your computer, using some photo editing software, and then save it at the smaller size you want to see it as before you upload it.

That's a very convoluted and poorly described explanation, but I hope it makes some sense.