Ideally, even for a "legit" recital, your theme should be "entertainment". This means structuring your recital in such a way so that it has high points and peaks as well as slower, more emotional moments. For a legit recital, this becomes increasingly difficult to do as the individual length of pieces increases. Sure, no one expects your recital to play out like a U2 concert. But theming your recital to be "Neo-Romantic trombone music of the mid 20th century" and only choosing pieces from that genre will produce a pretty flatline experience for the audience.
Some examples:
Any of the recital albums produced by Alessi clearly have had a HUGE amount of thought put into music choice and music order. Especially the "Return to Sorento" album. Contrast this to the BIS album "Solitary Trombone", which would be a very difficult program to sit through unless you specifically got to see Lindberg.
The album "Virtuoso Trombone" would have been an outstanding recital to see, however. From the first moment he gets you with something completely unexpected, takes you through some solid core rep pieces, and only after this point shows you something very outside the box with the Berio piece.
So, if you aren't Lindberg or Alessi, what do you do? You have a couple pieces you're great at, but where do you put them in your recital? What do you say, if anything, between pieces? How do you acknowledge the audience?
First of all, repertoire choice: Your opening piece must be your introduction to the audience and needs to grab their attention! Listen to the first track on "Criminal Trombone 1 1/2" or "The Virtuoso Trombone" or "The Burlesque Trombone". If you're at that recital, he's already got you. Don't start you recital by talking "Ah yes, in the, ah, early 20th century, blah blah blah." Honestly, even music professors don't care about that. It's not your job as a musician to educate the audience either. Start your recital with a short, exciting piece -- "this is who I am"
Then, after you acknowledge the audience and let them clap, that's when you talk. Again, not to educate anyone. Introduce yourself, introduce your pianist, tell the audience how excited you are for them to be hearing your music. Don't tell them the name of the next piece or who wrote it. Once you thanked them for showing up, just play it.
Piece two should be a core repertoire piece. Something that everyone would expect. It's not the time to bust out Sequenza V, or to play the random jazz tune you thought you'd throw into your recital. No, this is your slot to play Creston, or Sulek, or some other piece that tells a complete musical story. Again, acknowledge the applause at the end.
The goal is to build from your second piece towards a high point -- your most difficult piece -- either leading towards intermission or the middle of your program. Put the most exciting piece there, especially if there is an intermission. If possible, this piece should have a trashcan type ending that the audience undeniably understands as
"THE END!!!". You will get lots of applause after a piece with a trashcan ending. Think Blue Bells of Scotland, Great Gate of Kiev, the final movement of Tbone Concerto, etc. That kind of ending. Sure, it's cliche. Definitely is. However, the non trombone playing members of your audience who don't care about trombone music like you do are dumb, even if they have a PhD. They like exciting pieces with trashcan endings. They will (predictably) eat up any and all attempts to throw entrainment at them.
Now, if there is intermission, this is great. Accept the applause graciously, and then walk off the stage. Let the hall manager announce intermission. If you did your job the audience will be like "oh man, how is he going to follow that up?" or "oh man, where did he go? I want to keep clapping at that trashcan ending!"
If it's the middle of the recital with no intermission, accept your applause graciously. This is now your chance to talk to the audience. Tell them how happy you are that they are there. Tell them where you came from. Tell them about how music brings everyone together. Tell them something funny about how your recital almost failed in the rehearsal stages. Whatever you do, do not say "erhmm, up next we have a piece by Johann Sebastian Bach. Bach was-, blah blah, etc". Resist the urge. In this case, with no intermission, after you have spoken briefly and earnestly with the audience, you have a chance to play something for yourself. Everything you played so far has been to entertain them (or so you tried to make it appear), now it's time to play something for yourself. This is where that cool jazz tune you worked up, or lyrical melodic euph solo (song for lotta?) goes. The audience will buy into it now.
If there was intermission, when you come back you need to build the energy back up, so you need another short intro piece, like what you started the show with. No talking. When you get your big applause you can continue the recital as shown above.
You can keep the energy level low at this point. Put your melodic and contrasting pieces here. Create a "moment". If you were Bobby McFerrin, your audience participation would happen here, but that is super risky. Play it cool. Then ramp it up for the finale. Your final piece should also have a trashcan ending. Accept your final applause graciously for a bit longer than you did in between pieces, and then confidently walk off stage.
Phew.
So, it's not so much about what pieces, as much as it's about managing energy levels in your show. And it takes almost no effort to incorporate the most basic techniques from live music shows into your legit style recital and make it 1000% better than that other recital that might have been played flawlessly but was still super awkward and boring.