Here are the main guidelines for the logo image, which you can set in Theme Options » General tab.
No matter the dimensions of the image you upload, the theme will always limit the height or the width of the logo to make it fit into the header. That limit depends on which header layout you’re using.
Header Layout 1:
Limits the height to 60px.
Header Layout 2:
Limits the height to 110px.
Header Layout 3:
Limits the height to 150px and the width to 240px.
Header Layout 4:
Limits the height to 100px.
Header Layout 5:
Limits the height to 90px.
Header Layout 6:
Limits the height to 120px and the width to 220px.
Header Layout 7:
Limits the height to 80px.
Header Layout 8:
Limits the height to 124px.
To get the best results, upload an image that has the same (or a bit bigger) height and width as the limits on each layout, but never smaller than that.
If you also want to upload a version suitable for retina devices, then the size should be twice as big as the regular one.
We recommend using PNG with transparent background.