How have a image in the center of the dashboard header in Shinydashboard R?

Here you go

There is no way you can add the image to the header part on the right side with the function from shinydashboard, but let's have fun with the latest htmltools by injecting styles and tags into the header.

library(shinydashboard)
library(shiny)
header_img <- tags$img(
    src='https://cdn.vox-cdn.com/thumbor/Ous3VQj1sn4tvb3H13rIu8eGoZs=/0x0:2012x1341/1400x788/filters:focal(0x0:2012x1341):format(jpeg)/cdn.vox-cdn.com/uploads/chorus_image/image/47070706/google2.0.0.jpg',
    style = 'height: 50px; width: 100px; position: absolute; left: 50%; transform: translateX(-50%);'
)
header <-  htmltools::tagQuery(dashboardHeader(title = ""))
header <- header$
    addAttrs(style = "position: relative")$ # add some styles to the header 
    find(".navbar.navbar-static-top")$ # find the header right side
    append(header_img)$ # inject our img
    allTags()

ui <- dashboardPage(
    header,
    dashboardSidebar(
        sidebarMenuOutput("menu")
    ),
    dashboardBody()
)

server <- function(input, output) {
    output$menu <- renderMenu({
        sidebarMenu(
            menuItem("Overview", icon = icon("tachometer"))
            
        )
    })
}
shinyApp(ui, server)

The img is placed on the center of right side header, not the center of the entire header length. If you want to adjust to the center of the whole length, try to change translateX(-50%) of the img to a number you like.