Up until this month, I've always included the PNG overlay files with my Photoshop brushes. After much deliberation, I've decided I'm going to discontinue this practice. Let me assure you though that it's actually quite easy to make the PNG files if you need them.
With Photoshop CS6, we can now create and use brush sizes up to 5000 pixels large compared to earlier versions that limit the size to 2500 pixels. While this is wonderful for us designers, as a creator of brushes I've been struggling with how to deliver the much larger file sizes. The file sizes can be 5x larger. I recently created a CS6 brush set that ended up being 500 MB large. If I also included PNG files and CS2 & Elements version of the brushes, the download would have been over a GB. This one brush would take up 1/10 of my current size limit for my store downloads! As a vendor, this just isn't feasible. I would love to provide my brushes in the larger sizes, so I've been mulling over how to handle this. (I actually have several sets of brushes waiting to be released until I figure this out!)
Let's first go over why PNG files are normally included. When creating Photoshop brushes, they are not backwards compatible. I my create brushes in Photoshop CS2 to have a larger range of compatibility, but a person using Photoshop 7 will not be able to use them. Also, people using software such as PixelPaint Pro will not be able to use the Photoshop brushes. As a courtesy, up until recently I've included PNG files with all of my brushes. Note: Generally Photoshop Elements 6 and above can use my brushes.
There are several factors I've taken into consideration to discontinue PNG inclusion.
For now, most of my brushes still come with the PNGs, but I will be updating the downloads within the next few months.
I do hope this doesn't disappoint, but these decisions will allow me to offer more products while keeping my brush prices reasonable.