You could always make a traditional simnel cake, but these are quite difficult. For a much easier Easter cake you could try and idea from chef Hugh Fearnley Whittingstall: you make a typical sponge cake (in two layers, like a Victoria sponge) and then you take some bits of chocolate from Easter eggs, plus some little chocolate mini eggs, crush them and put them between the cake layers. Then put in the oven for just a minute till the chocolate melts. This can be eaten warm as a pudding or cold as a cake (when the chocolate has gone hard again). You can find the original recipe here.
Or for a newer idea you could try making brownies with chocolate cream eggs inside them - you put the eggs in the freezer first for a few hours so they go hard and don't melt when the cakes are cooked. The recipe is here.