I have a lot of old t-shirts that I no longer wear, but have sentimental value. I’m looking for a way to repurpose them. My searches so far have led me to custom made quilts, and wall art.
Any other ideas?
Throw pillows.
Well, that’ll make me feel better for a little while, but then what do I do?
Oh. 
Take a pic of you wearing them and make an album of why they hold meaning for you. Then turn them into cleaning rags. It’s the memory you want to keep, not the fabric.
Those quilts are pretty cool but can be expensive. Rightly so - I’m sure they take some time to make!
I made wall art from mine. You probably saw this already - I took record album display frames and folded & taped my shirts up in there and they look great. Some tutorials suggest cutting your shirts but I said no way! My shirts are XL and XXL and fit just fine, FWIW.
This.
I keep a box of old t-shirts for cleaning after painting or working on the car.
They’re great dust rags too.
We re-purpose them as grocery bags. I’ll try to describe the process: Cut off the sleeves. Sew the bottom together. Then trim the neckline to be a bit more open. If this is too confusing, message me and I’ll try to send a picture. They are amazingly strong and have a huge “carrying capacity.” Here’s a video: How to Make a T-Shirt Bag - YouTube
You can make a blanket instead of a quilt. Much easier to do and less time consuming. The cost to make one isn’t nothing, but it’s fairly small.
Cut off the design and save it for pillows. The rest of the shirt you can make t-shirt yarn and crochet it or weave it into a rag rug.
They are great pulled over silhouette targets for practical shooting. Adds that nice touch of realism and hides the A zone.
By the way it appears you cannot Google this even though many a pistol competition uses them this way. All you get are images of T shirts with targets printed on them.
Dennis
Teen-age girls made skirts out of them, back in the nineties.
We have two of the quilts. We love them.
I have a quilt/blanket; it’s t-shirts with a fleece backer. Can be anywhere from sofa throw to king size bed. If paying for it, shop around as pricing can vary greatly; one place can be double the next.
One of my Facebook friends - a woman I worked with many years ago - recently posted pictures of the t-shirt quilts her late ex-husband’s aunt was making for their sons. Those quilts will probably outlive her sons, who are both 30-something. He had a lot of Nascar and concert shirts, and attended a lot of those events with the kids, so those memories are very precious to them.
The cloth between the t-shirt graphics came from the shirt backs or sleeves, if they were plain, or his other shirts that the sons didn’t want to wear themselves.
If she was charging for it, it would probably cost a fortune. I do recommend getting several quotes if you want to do this.
This and I made a few into drawstring bags. A friend with a drop ceiling in his basement/rec room covered some of the panels with his “heirlooms”. It actually made a nice little display and added something of a warm feel to the space.
The quilts are very easy to make. Just cut out the sentimental part of the shirt into squares & sew them together. It’s all straight lines, so if you know someone with a sewing machine, they could put it together in about an hour,
You would think it would be easy. But there are factors to sewing stretchy material. Some of the shirts will be of differing weights. It surely can be done by someone who knows what they’re doing. But, easy? Not exactly. I’ve made several quilts.( not t-shirt quilts) The size alone creates problems. And then there’s the quilting. I know a couple of ladies who have a longarm quilting machine. They quilt for a fee. They wouldn’t take a t-shirt quilt. Too many variables.
Hmmm I am not a seamstress, but my friend made a quilt for her son when he graduated high school & she described it as very easy. But now that I’m thinking of it, she didn’t make his out of tshirts, but all his sports jerseys. Maybe they are easier to work with? And maybe it wasn’t considered a quilt, but a blanket? I’m really not sure of the difference, but after you brought up “quilting machines” which I’ve never heard of–she used a regular old sewing machine-it occurred to me I might be talking about something else. 
A blanket is one layer of fabric. A quilt is 3 layers, a quilt top ( the t-shirts) a layer of batting and a back. They are quilted togeter, which means sewing through all the layers. A comforter is a quilt with very heavy or fluffier batting.
Quilting(sewing the layers together) can be done with just a thread and needle. Takes forever. Purists believe that’s the only way to do it.
Is there a way to cut around the design and then attach it to a new t-shirt?