Hmm....well I know how to do everything with Photoshop, but I'm pretty sure it's the same in PSP
To make the brushes compatible with PSP7: Well, I think they should be automatically, if you make them in PSP 7... I'm not exactly sure since I don't use PSP anymore
However, to make an image pack, just create a new blank image with a white background. Then use all your brushes in black on the image, making sure that the brushes don't overlap. Just save as .jpg
And to upload them onto your site, you can either just upload the .jbr file (like Mae said) or you can save the image pack and .jbr file into a .zip file and then upload the .zip file

Then whenever someone clicks a link to a .zip file, the download starts automatically
I hope that made at least some sense
