Three suggestions to spice up the current dye selection:
1) Add the fixed dye gachapons that lorna sells in live. (
http://wiki.mabinogiworld.com/view/Fixed_Dye_Gachapon#Green_Fixed_Dye_Ampoule_Gachapon) A few more hexes to each selection would be nice, such as #191919 and #e6e6e6 to black dye gachapon, #524782 to purple, #EB731C to yellow, etc.
2) Seasonal and holiday dye gachapons. Summer dyes, Christmas dyes, Halloween dyes, Easter dyes, Winter dyes, etc. Just a little something to help fit the seasons or the holidays. Plus it's an easy rotational 'content' addition.
3) Import Spirit Weapon Custom Color Dye Ampolues. I'm sure many would love to be able to dye their spirit weapons, and these are the only way to dye most bows and wands currently.
Please don't add anything to the regular fixed dye gachapon though. That gachapon is cluttered enough as is. Separate dye gachapons would be much more popular.