I would double-check the rules, but once you have marketplace access, some people offer these services under the "Customizing Services" tab. Technically, all talk of purchasing should be regulated to the Marketplace, but I'm not certain if customization requests (the mods) actually count. I do know that people who do customizations cannot tell you that they do them/are open for business because that violates the rules.
Members with Marketplace Access who offer services through the Marketplace cannot offer their services to anyone without Marketplace Access here on the forum. That would be in violation of forum rules. Rule number 6 states: Members can answer your question by telling you about faceup artists and customizers they know about who commission offsite. Most of the faceup artists I work with I am in contact with and follow via Instagram~