Youre trying to fit too much in too small a space Blaze, start with a 550x200 blank image and compose it, maybe go for one or 2 figures instead of 6. Try showing only the top halves of them as well with the rest hidden off the bottom of the image so you can have the figures a bit larger. Having the feet hidden off the bottom also avoids the fact that they look a bit odd being lighter than the background with no shadows.
A tip is to get the objects from model viewer at a higher resolution and shrink them down to the image too.
If youre suffering from artifacts, try saving in .png format as well rather than .jpg.
Looking at your current sig Blaze, you might want to use the full width allowance, 550 pixels that you have rather than cramming so much so close together.