BIP-39, uses 2048 words, and can all be distinguished from each other using the first four characters of each word. This is used to encode raw binary entropy, but adapting it to arbitrary amounts of data is straightforward. For padding I would suggest either pre-encoding length at the start or using classic block cipher padding (https://en.wikipedia.org/wiki/Padding_(cryptography) )

See for BIP-39, wordlists under a folder https://github.com/bitcoin/bips/blob/master/bip-0039.mediawi...