Judging by your "abstracted" email, I'd say you could eliminate quite a few I's by either resorting to bullet points or by making your sentences longer. Simply provide a series of actions you took, separate them with semi-colons, and place the I either before or after the list. For example (with the I before the list),
As you've requested, I've done a number of things to devise a logo, including playing with fonts and texts to find an appropriate one; choosing a strong, uniform font to make the text memorable; using a minimalistic--but distinct--style; incorporating into the logo a shape; and experimenting with a number of different designs and different backgrounds for the logo.
An example with the I following the list:
Playing with fonts and texts to find an appropriate one; choosing a strong, uniform font to make the text memorable; using a minimalistic--but distinct--style; incorporating into the logo a shape; and experimenting with a number of different designs and different backgrounds for the logo are a few of the steps I've taken to provide you with the logo you've requested.
Of course you can accomplish the same thing by using bullet points if you deem them appropriate for this particular email.
By the way, you needn't combine every action you took into one sentence with numerous semi-colons. You could mix things up by doing something similar in two or more sentences. The point is this: By providing a list and then putting the I either before or after each list obviate the use of too many I's.
Just make sure that each item in your enumeration of items begins with the same verb tense in order to maintain parallelism (e.g., used . . . used . . . used; using . . . using . . . using; making . . . making . . . making; designing . . . designing . . . designing; and so on).
