To add a level of difficulty. I would add number cube to see how many letters to cover up at a time. Use tally marks, dots, numerals ect Free "find the letter" alphabet worksheets! Get them for uppercase, lowercase, and both!
If you're teaching your toddler the alphabet, you'll want to check out this huge list of playful alphabet activities for 2 year olds! While learning the alphabet, kids had opportunity to learn new words.