The first thing that pops up in my mind when someone says leather is actually the smell of vegetable-tanned leather. The second is the patina. The development of the patina on leather is a beautiful sight. It takes a while for the patina to develop significantly, usually weeks or months. But it's worth it.
I've blogged about Patinas a while back here with pictures in it. I can never get enough of visuals so here's a few more!
This is an LV bag that has developed a really deep Patina over 5 years or more.
This phone pouch has developed a nice Patina (though not as deep as the LV bag) over 3 to 4 months of usage. I've placed a brand new piece of vegetable-tanned leather from the same hide used for the pouch to show you the difference.
Another option is of course to DIY-it. You can create an artificial patina using oils and polishes that can almost look like the real patina. Nothing artificial can beat the look and feel of the real patina, but this is something worth trying if you want to change the look of your brand new bag, shoes, wallet and other leather accessories in the shortest amount of time.
I came across an article, "DIY Vintage Leather Patina" from Lauren Moffatt's blog on using olive oil to develop a nice light patina on a pair of vegetable-tanned Swedish Hasbeens. The article gives great instructions on achieving the look.
There are also other oils that you can use such as neatsfoot oil or even vegetable oil! You may need to apply a few layers, dry it out in the sun and re-apply again to obtain a deeper tan. In time, with use and touch, it will gradually develop a natural Patina as well!
Whether you let your leather item develop naturally or use oils to develop a Patina, it will definitely give a certain unique character that is different to any other!