Maybe it would be useful to list some of the types of concessions and perks suppliers will sometimes offer. I'm sure there are others I've never heard of, but I am a very small player.
Free UPS or other shipping, for example, with five chops. Sometimes this is listed, and sometimes you have to ask.
Better price breaks. For example, 10-case pricing with 5 cases of glass or 5-case pricing with a single case of fomeboard.
Better pricing if you commit to a certain minimal purchase volume each month.
Free corner samples.
Longer payment terms on major equipment purchases, and/or shipping allowance.
Substantial price breaks with exclusivity. For example, if you show only one mat line or one metal moulding line. (This one makes me nervous.)
When I was still selling photo supplies, it was common for vendors, like Kodak, to offer coop dollars to help pay for advertising if it included a logo or a mention of their products. I've never heard of this in our industry, perhaps because we don't have the brand recognition that Kodak and Fuji enjoy.
It's unclear whether you are a brand-new business owner or an old pro looking to cut some costs, so I apologize if this is all old news.