I am having an issue of the cars not showing up in the damage gallery. This happens when I play in 3dfx mode. Does anyone know what's going on?

This is known problem described on official Carmageddon site (carmageddon.zendesk.com/hc/en-us/articles/200942341-Carmageddon-Max-Pack-Known-Issues). However some of listed problems are already fixed in unofficial patches or with external tool. I think this may be issue of 3dfx.exe, so using voodoo exec instead may help. I can't check/test this here, but I think you may try to install 95RPP (Unofficial Max Pack 95 Restoration Project Pack) which using voodoo exec by default.