User account image resizing issue.

When I choose a new picture it automatically resizes to 128 x 128. My problem is that when you click on the image to login, it increases to what seems to be 256 x 256, but rather then using the source image and resizing that it appears to just scale the 128 x 128 image up, leading to a terrible looking image.

I figured that I might be able to get around this by seeing how the default images work since their larger versions look fine. Looking into the C:\ProgramData\Microsoft\User Account Pictures\Default Pictures all of the images seem to be 128 x 128, so I figured that there must be another folder with 256 x 256 versions of all these images for when the larger image is displayed, but am unable to find such a folder.

So basically my question is, is there anything I can do to have a decent quality image for my account image?

Sorry, I mean that when I initially start my computer, I am greeted with the login screen. Once I click on a profile picture, the picture is then scaled upwards and put into the center of the screen, and I am then able to enter my password.

Not sure how to adjust the quality of a bmp. From what I understand bmp does have the option to save as 1, 2, 4, 8, 16, 32 bbp, but I don't know what type of image editing software I would use to do this, I am currently using Gimp, which generally gives a good range of options when saving in various formats but in the case of bmp seems to just allow me to choose to use RLE algorithm or not. My limited understanding is that the RLE algorithm is a 8 bit compression algorithm, I could be wrong though.