The tattoos on your back (and my back!) and your ankle should be fine.
Your tattoo on your thigh may end up looking a little funky and here's why.
As you lose weight and exercise, your skin may "tighten" (due to a hormone that is released).. since your tattoo is part of your skin, it could end up looking a little wierd... but my friend says her dad lost 100 lbs and had a tatoo on his stomach, and it just got a little squished.
It also depends on your age (older you are, unfortunately, less your skin will "tighten") and if you got the tatoo before or after you gained weight.