We are using a rotating header on our site - www.ospdirect.com. All images are PNG's 1080 x 180. When using the GTMetrix speed test, the result is the header images(s) are missing width and/or height attributes. It is my understanding we need to specify the width and height of all images, either in the HTML <img> tag, or in CSS to correct this loading/speed issue. I am not sure how to do that within Atahualpa.

Any advice or suggestions sure would be appreciated.

I personally don't pay much attention to the speed test sites. There are too many variables. If you want a really fast site make sure you are on a private server, your images are on a CDS all of whidh costs $$

the rotate/cross fade is done via jquery

you could try adding

#imagecontainer img {
    height:  180px;
    width: 1080px;
}

to the CSS inserts and see if that resolves your 'warnings'