The thing to remember is that fabric runs on a season just like clothing and what you see now may not be available next month or next year. My rule is if I love it I buy some of it even if it is only quarter yard. (That is why my house is over flowing with fabric) If I am out shopping I take a picture of the info at the top of the bolt so that I know the designer and pattern name if I want to buy more later.
Much of my fabric is quilting quality fabric as it is a better quality and comes in a huge variety. This also means that they are cotton and run $9-$11 a yard.
Within the quilting/cotton fabric collections one of my favorite designer is Timeless Treasures. Over the past 18 months they have had several patterns that have a steampunk aesthetic. Check thier website for stores near you that sell the fabric, if you are going to buy a larger quantity your local quilt store might give you a discount that online stores don't have.
My favorite designs by Timeless Treasure include:
That is all I have to show you today but I will continue to post more fabric options. If you know of a great steampunk fabric please post it in the comments!