SO the new T&C just went live and the part the will impact almost everyone is:
(TLDR: Not lego = not allowed, including custom printed, chromed and light kits)
Items for Sale:
If you are a registered seller on the Site, you agree to comply with the following rules for selling. We reserve the right to delete without notice any items listed in your store on the Site that in our judgement do not comply with these rules. Repeated violations of these rules may result in the suspension of your selling privileges.LEGO Brand Only: All items listed for sale must be LEGO brand products unless they fall into either of the two categories listed below – 6. 2.5 (Custom Sets) or 6.2.6 (Non LEGO Items). Other brands of building toys are not permitted.
Items Pending Official Release: Items may not be listed prior to their official LEGO release date, either as custom lots or under related catalog entries.
Replicas and Counterfeit Items: All LEGO items must be original and genuine. Replica boxes, photocopies of instructions, or any other counterfeit listings are not permitted.
Modified Parts: All parts listed in your store must be genuine LEGO parts in their original, unmodified condition. Custom printed, engraved, chromed, or painted parts are not permitted.
Custom Sets: Custom sets or instructions may be listed, provided they do not infringe on any intellectual property rights, including those of the LEGO Group. Custom sets may not contain modified parts or non LEGO parts such as lighting kits or electric motors.
Non LEGO Items: Certain non LEGO items that are deemed by BrickLink to be part of LEGO fan culture may be listed. These include literature about LEGO products, LEGO memorabilia, and items used to make custom sets (e.g. stickers, instructions, and boxes).
No Animated GIF Files: If you are using your own image of an item, the image cannot be an animated GIF or the animated GIF must contain only 1 frame.
Exact quantity: The quantity of the item that you are listing for sale must not be greater than the quantity you have on hand. The only exception to this is a custom LEGO magazine that has to be pre-ordered and the buyer is made aware of this in the item description.
Comments Field: You can include the price of the shipping costs in the comments field but you can't hard-code the price of the item for sale in the comments field. Putting an exchange rate in the comments field is prohibited.
Item Condition (New/Used) and Sub-Condition for Sets (Complete/Incomplete/Sealed) must adhere to their respective Definitions. Sets which have been previously built must be listed as Used. Sets without Minifigs must be listed as Incomplete.
MOC Packages. If you offer for sale in your store bricks and build instructions for a design made available by a designer (a “MOC Package”), then you must (i) offer to sell all the bricks that are necessary to build the model represented by the MOC Package and (ii) deliver or otherwise make available to the buyers of the MOC Package the build instructions for the MOC Package.
Designers’ MOCs and Designs. Without written consent of a designer, or except as otherwise permitted herein, you may not sell, reproduce or create derivative works of any designer's models, images or designs published on the Site, including at moc.BrickLink.com or within the Studio Gallery portion of the Site.
Compliance with Laws. You as a seller agree to comply with all applicable laws, rules and regulations, including without limitation all laws regarding ecommerce, distance selling, consumer protection, commercial electronic messages, privacy, disclosures that must be made to buyers in advance of a sale (including without limitation the terms and conditions applicable to each sale), affording buyers’ the right to review, accept and reject such disclosures, and providing to buyers copies of the terms and conditions of sale.
And for those thinking i'm not a seller this does not impact me: if sellers can't sell something, buyers can't buy it