Will this work for a university lecturer, not just a school teacher?

It can, though the classroom setting and cardigan lean toward a school context; a university bio might sit better with a more neutral look from this group depending on the department.

Can I keep my own clothing instead of the cardigan?

Not in this look, the wardrobe is fixed to keep the warm, approachable feel consistent across everyone who uses it.

Is a big smile going to look unprofessional on a staff page?

Not for this context. A school staff page is one of the few professional settings where a broad, open smile reads as exactly right rather than too casual.

Teacher headshot

A friendly portrait in front of a classroom.

8 photos

A school staff page is read by parents deciding what kind of person is going to spend the year with their child, and by students scrolling past looking for a familiar face before the first day. Neither of those audiences is looking for corporate polish; an overly formal photograph can actually work against a teacher's page in a way it would not on a law firm's site.

This look is built around warmth and immediacy rather than gravitas. The classroom behind the subject holds a blurred bulletin board and a stack of books, lit by bright, even daylight pouring in from a bank of windows rather than a studio softbox, which keeps the setting feeling like an actual classroom rather than a staged backdrop. A soft cardigan in a warm coral tone replaces a blazer, and the pose leans slightly forward toward the camera, a small physical cue of engagement, with a bright, open smile that reaches the eyes rather than a composed, closed mouth one.

It fits a school's staff directory, a classroom door photo, or a district website bio, and it is built to answer the actual question a parent or student has when they look at it, which is simply whether this looks like someone approachable.

What makes a good photo to start from

A photo with an already open, engaged expression gives this look less distance to travel than one with a flat or tired expression, since the whole point of this style is warmth rather than formality.

What this look will not do

It cannot place you in your actual classroom, with your real bulletin board or your students' work on the wall, and it will not add a school's specific colors or mascot, since none of that exists in your uploaded photo.

Questions

Will this work for a university lecturer, not just a school teacher?: It can, though the classroom setting and cardigan lean toward a school context; a university bio might sit better with a more neutral look from this group depending on the department.
Can I keep my own clothing instead of the cardigan?: Not in this look, the wardrobe is fixed to keep the warm, approachable feel consistent across everyone who uses it.
Is a big smile going to look unprofessional on a staff page?: Not for this context. A school staff page is one of the few professional settings where a broad, open smile reads as exactly right rather than too casual.