Is it possible to make custom addresses? And if so how?
You can use Pascal’s Address Miner to generate custom addresses. Up to 4 letters are pretty quick, more letters take longer to find.
Since addresses are derived from your public key, the only way to create a custom address is to mine one. That means you just create random private/public key pairs and check whether the address matches your wishes.
Obviously, it is computationally impossible to mine a full custom address (if such a generator could exist, I could simply generate the private key of any address and steal funds ).
As @NimiqSoeren already linked, you can however use my vanity miner to create addresses with a given prefix.
The Bitcoin wiki features a nice table with time estimates to find the private key to a given prefix of length n: https://en.bitcoin.it/wiki/Vanitygen
There is a new version of the vanity address miner to be found here.
It supports the new KeyGuard’s key derivation and multithreading.
Upon finding a match, it outputs the 24 words required to import it into the Safe.
Still, it is much slower than the old address miner due to the fact that key derivation takes some time.