OSB board will do the trick. You need another photo for us to offer a species and finish. Natural finish (clear coat...water based polyurethane finish...NO oil modified) in a low gloss or satin finish on white oak with FLOOD LIGHTS will offer the same "look" as the poor photo. Beyond that, you will need a better photo.

Is there a reason you have those colors on the walls? Without pics we are in the dark. What exactly is your style ?

Hi Esha, One option is of course to highlight it, as rightly pointed out by Hyphen Designs. The other is to add more beams to the ceiling and turn it into a design element for your space. Attaching some pictures for your reference. depending on the look of the space - you could choose how rustic you want to go with the kind of wood you use. you could clad the existing beam in wood and add maybe 2-3 more to introduce a pattern through repitition. if you find solid wooden beams a little too heavy, you could let them be finished in POP and paint and add some wood only at the base - just to create that highlight. and if you're ok with the wood - you could also probably add more beams than just 2-3 and give the ceiling a distinct look - like in this picture depending on the furniture layout you could highlight the singular beam in your room by painting it another colour or better still - i would stick to wood and maybe hang some lights or a nice installation that would add character to the space. if you dont like the wood.. you could probably add split levels to the ceiling coming out of the beam and highlight them by introducing some indirect tray lighting that would accentuate the levels. hope this helps!

Nadia, You need to provide some more snaps showing the entire room, including the location of the beam, its height & clear height of the slab etc. One idea could be to extend the width of the beam by just about 25 mm with gypsum board on either sides, at the bottom level, with a right angular vertical of 25 mm as well & provide LED lighting strip for indirect lighting...